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JohnsonGunsmith
05-25-2011, 12:22 PM
Who is doing or ha done vibration testing with accelerometers or other methods on barrels etc? I have read Harold Vaughns book many times but I want to do some of my own testing and not waste $$$ in the process. I need to know if anyone else is doing or has done this type of testing so I can be as efficient as I can be without negative effects to the results. I am doing all I can to make my bench guns shoot better and would appreciate any help as to who to contact so I can do my own testing while not making any large mistakes in setup or equipment purchase. Also if anyone else is intrested in this type of testing and work I would appreciate your input/help. I am attempting to make a name in the business and the results will be used to benifit all shooters. I appreciate all the help and knowlege I have recieved from this website and would love to be able to give back something and hlp move Gunsmithing and the sport of Benchrest shooting forward.
Thanks in advance
Brandon J.

Lawrence W.
05-25-2011, 01:12 PM
Varmint Al has done a ton of this stuff. http://www.varmintal.com/aeste.htm#Ladder . One of our local shooters, Don Jackson would shoot our matches with all sorts of accelerometers hanging off of the gun.

JohnsonGunsmith
05-25-2011, 03:33 PM
I have been to His website and I find it very useful. It is mosty full of raw data for tests he has done and not as much on the equipment he uses etc. I could be very wrong and will go back and look at his site because I might have just missed that part somewhere. I also will try to contact him and see what I can use from his extensive testing to help me with my future testing. Thank you Lawrence and I will try to get in touch with the persons you mentioned and see what they have to say. I appreciate your help.
Brandon J.

jackie schmidt
05-25-2011, 04:54 PM
Johnson, please do not think I am being trite, but have you thought about installing a tuner and simply skipping all of the conjecture.
.......jackie

Boyd Allen
05-25-2011, 05:51 PM
In the past, I have emailed Varmint Al, and he responded. If you look on his web site, I think that there are directions on how to email him. I believe that he uses a title line phrase as a spam filter.

JonathanK
05-26-2011, 01:44 AM
I have always wanted to use a high speed video camera to see exactly what the barrel does when fired and the position of the barrel at different nodes and between nodes......These are still pretty expensive though

frwillia
05-26-2011, 09:06 AM
I've done a bunch of testing but not on rifle barrels. Couple of things to keep in mind when considering methods:

Any mass you add to the barrel anyplace, in the form of accelerometers for instance, will influence the results, how much will depend on location. Unfortunately, the locations with the most movement which give the best data, are also the locations which will have the most influence on the response of the system being measured.

Duplication of initial conditions is absolutely essential to transient measurement of any dynamic system. If the initial conditions aren't the same from test to test, the system response won't be repeatable. The implications of this will have profound impact on the design of the experiment - both for getting data and for the data having meaning when applied to a particular shooting situation.

Fitch

JohnsonGunsmith
05-26-2011, 09:34 AM
Thanks Fitch I have considered this and how I think about it is we have changing conditions and I need to know what happens in each of the conditions so all the results would be valid and repeatability should be important only if the conditions are exactly the same and all the variables are the same etc. This not being 100% possible it is a try to see the big picture kind of process. Nothing in life is 100% anyway except for death so I am just thinking of running with it. I hope this does not sound like I am ignoring your advice because what you said is valuable to me and I appreciate your help. I understand that you have experience with this type of work and I do not. That being said I place a high value on your suggestions because you know more about this type of work than I do and I do not pretend to know better how to go about this testing.
My focus is on the Vibrations and dampening them. I am focused on consistency and vibrations can hurt you since there are always variables to consider. A gun that vibrates less should be effected less from the slight inconsistencies that we all impart on the gun because we are not machines. This will allow the gun to fire more consistently because the vibrations are less severe so any effect we have on the gun in the shooting process will not be magnified by the vibrations thereby increasing the consistent nature of the gun. I hope that makes sense and describes my intent more fully. I would like to hear more from you guys and all your advice so far has been great.
Thank you all very much,
Brandon J.

Vibe
05-26-2011, 10:21 AM
[B]Who is doing or ha done vibration testing with accelerometers or other methods on barrels etc?
Brandon J.
You might pose the question to Dr Geoffe Kolbe of Border Barrels as he has done (and is in the process of doing more) extensive work in this area.

frwillia
05-26-2011, 01:27 PM
My focus is on the Vibrations and dampening them.

What you are concerned with is the motion that preceeds the bullet leaving the barrel - nothing after that, other than the rifle system resetting to the same initial conditions before the next shot, matters. The best program for dealing with it is to design the rifle system so it's unconstrained behavior results in an acceptable motion. This can be done in part by the design of the rifle (free floating the barrel to make the response the same simple harmonic function each time, and stress free bedding to give equivelant initial conditions prior to each shot, etc.) and fine tuning by choosing a load that gives the most consistant performance (smallest group).

Additional mechanism can be added in the form of a barrel tuner (adjustable weight) but if this added complication (which is "not" damping) can be avoided, especially on a hunting rifle, it is better.

Trying to modify system behavior by "damping" vibration requires using some mechanism to absorb energy from the system in such a way that it causes the systems vibrations to decay faster than would happen if the energy wasn't removed. Damping (think something like the shock absorbers in a car) can cause a whole new set of problems since it has to be done in such a way that the consistancy of system response and initial conditions aren't disturbed.

The KISS principle applies.

The other issue is to design the testing so that it applies to more than just the system used in the experiment. What you are looking for is proof of general principles that can be applied to more than one particular test article. Testing every possible system, or even one system in all it's possible conditions of use, is a practical impossibility.

At this point in the development of bolt action rifles, I suspect the incremental rate of return measured as group size reduction per dollar spent on testing would be a rather demoralizing number.

The best way to see the big picture is to do the analysis like Varmint Al did (he's an expert at analysis), then do some measurements to confirm what the analysis is telling you.

Fitch

David Merrill
05-26-2011, 02:12 PM
Some interesting reading for you.

http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA162135

http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA201713

http://www.arl.army.mil/arlreports/2000/ARL-MR-492.pdf

http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA474853

http://www-personal.umich.edu/~cwkauff/Aero729/file/PRODASV3%20User.pdf

Note mentions of 'muzzle jump' and 'aerodynamic jump'.

David Merrill

JohnsonGunsmith
05-26-2011, 04:04 PM
Fitch you are correct about the $$ to benifit ratio on this deal. I appreciate your information and agree completely with all of what you say. I just talked to someone about building the systems to do this with and he guessed over $10,000 to buy equipment. That has me rethinking everything because my initial reseach showed 3-5K and that was acceptable if I could learn something but over double the price has me thinking it is not worth the investment. I am still working on some new ideas but they are more playing and not really on the level of serious accuracy inhancements. So back to the drawing boards I guess. I might try to rent some of the equipment in the future since I have found a place that does this. That would be much more cost effective. thanks for the websites david I will read them today. and Vibe tanks for the extra contact I will try to get in touch with him in the future.

4Mesh
05-26-2011, 04:58 PM
I just talked to someone about building the systems to do this with and he guessed over $10,000 to buy equipment. That has me rethinking everything because my initial reseach showed 3-5K and that was acceptable if I could learn something but over double the price has me thinking it is not worth the investment.
Thats insane. You've not said what equipment you have, but you should easily be able to get the tools you need (used) for <10% that. If I was starting with no equipment at all I bet I could be in under a grand. And, it's not like you finish up with the barrel crap and the stuff is useless. It is re-sellable or multi-use for other kewl stuff.

If you're at all experienced with embedded systems, you can buy a dsPic that'll do 9 simultaneous A-D's at 4Mhz 12bit res, for $5. There is a minimum order tho, you need to buy at least 2.

As it's a ds chip, and has many ds functions, it's fast as hell, programmable in C or assembly (all tools free except the programmer), and you won't feel so bad when you let the smoke out of one. Using a circular buffer you could set up your own post trigger for when the bullet leaves, you'd be set. It's got plenty of ram for what you want and you can add more for a buck or two. I've had these running at 160Mhz on a breadboard, stable, and with <.001vdc float on the adc channels, all channels measured simultaneously.

Do you have a scope? Is it a storage Scope? Even if you go brand new from Tektronix you can be into 4 channels for about $2200 and that's with a lifetime warranty. Way fast enough for what you want too, and again, can be resold for damn near new price.

I wouldn't chicken out just cause someone says it's expensive. I'd just shop smarter.

JohnsonGunsmith
05-26-2011, 06:06 PM
That sounds more like it. I do not have any of the equipment yet. I do not know why it would cost so much either but I was really discouraged after talking with him. I do not know what I am doing at all and am learning what I need as I go. Some of the things you said to me in the last post was over my head but I do understand the don't chicken out part and If I can do it for under $3000 I would be very intrested. Can you send me info. to get to the correct websites and places to get what I need? I am intrested and want to do some testing. I will be posting results on here after testing if it gets off the ground.
Thanks for the positive feedback and I feel like it is a possibility again.
Brandon J.

Charles E
05-26-2011, 06:27 PM
This is a complicated issue, and I'll probably make a hash of trying to explain where I'm coming from. But that never stopped me before . . .

People like Varmint Al are trying to model a system, so that what is learned can be applied to more than one rifle. But the number of variable are just too large. Any number of physicists have said "oh, it's easy, I'll have a product out real soon now." And of course, nothing emerges.

On the other hand, testing one rifle will let you make improvements, but how to extend them? For example, one of the variables is bolt thrust, and that depends not only on lug fit, but on how you resized the brass, etc.

It is one of my favorite analogies. Imagine doing the testing with a free-recoil muzzleloader, where the variables really are just the barrel (I think). Then repeat with a bolt gun, or some other form of breechloader. That will begin to show how much the action and cartridges affect the system.

Vern
05-26-2011, 08:21 PM
Question:
I am not sure if this applies to dampening or not BUT if it does....
On a rail gun the barrel is usually held in place with a block of some sort....and the action hangs off of the back end.
This being the case dampening or tuner is it possible to change the position of the barrel in the block to create a dampening or tuner effect?

4Mesh
05-26-2011, 08:39 PM
Well, I had about a 20 minute post binned by a power outage and what may have been a tornado. Not that I'm the most experienced person on such things, having only been front and center in two, but it was exciting enough to get me to the basement in a hurry. Wow, that came in faster'n anything I ever saw before. I have to assume it wasn't a tornado since the two I have been in gave all sorts of warning. This, I expected things to be removed from the house before I could make it down 2 flights of stairs... 30 min before was out mowing the grass and it was beautiful. :confused:

Anyhow, Charles, you should probably avoid these thread cause any minute now the post police will be stopping in to give you all sorts of flak for having an opinion, and then sharing it too. omg, How dare you! :p

I'm pretty much supportive of anyone who actually WANTS to find answers, and is willing to not just 'wing it'. Have you ever attempted to test something gun related and failed to achieve the desired result? Did that make the testing any less important, or dissuade you from trying the next thing? nope. I'll allow, this isn't an easy undertaking but mostly, I think I fall into the category of folks who things that the technology is there and that yes, it is easy. However, that is the part that is easy. Building the mechanical device that allows measurement, A-without influencing the result adversely, and B-can eliminate the S/N ratio coming from the Z axis, well, that's not so easy.

Anyhow...

Brandon...

Have you done any programming?
Experience with electronics?
Is this something that interests you enough to make up for the lack of the previous two?
Do you have any idea the learning curve it will take to do this if the first two answers are no?
Do you think I am implying that makes it impossible, or even unlikely?
Are you willing to spend $3-400 just to see if this has the slightest possibility of success?

So, then I'll just ask, what tools are available to you now? Check this list...
Decent quality Digital Multimeter?
Oscilloscope?
Digital Storage Scope?
Signal analyzer?
Breadboard? Solder Iron?
Milling machine?
Lathe?
Drill Press?

Are you at least passingly computer savvy? Meaning, not afraid of anything? I'm flying blind here so any of these answers would be a great help in saying what direction to go. Work can be made up for with $$$. Conversely, $$$ can be saved with lots of work.

Last but not least, Are you interested in seeing what these vibrations do, or are you actually interested in seeing if they exist and if they can be quantified, and their results quantified? I'll assume since you brought up Harold's name that you noticed in the book he used no tarot cards or voodoo dolls to find answers. He also didn't see things and attribute them to what he wanted them to be (as some around here do). He isolated the problems and quantified them, then decided what the big fish were and what the little fish were.

Regardless of what path you decide to take, I think the $$$ figure in question should ride somewhere around a grand, and that spread out over a fairly long time if you are frugal with $ and thrifty with time.

4Mesh
05-26-2011, 09:02 PM
Brandon,

While, this is not the ideal processor for what you're looking to do, and is no substitute for the right stuff, it is dirt cheap, and is everything you need to get started the "hard work, low money" way. If you can conquer these two things then this barrel deal will be a breeze. The chips that go on these boards are no where near the speed of a dsPic, but you absolutely could hook this to a gun and do serious testing. And, there's 2 spare boards to mess with later.

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en538340

http://www.microchipdirect.com/ProductSearch.aspx?keywords=DM164130-4

Vern
05-26-2011, 09:03 PM
Can you dampen vibrations by using a very THICK heavy rubber bushing placed and moved up and down the barrel?
I have wanted to try this in the same manner as a tuner.
I know you can find the sweet/dead spot by tapping on a barrel and listening to it.

4Mesh
05-26-2011, 10:22 PM
Vern, they sell gizmos specifically for that. I forget the name of the company, but they make various other gun products as well. Like recoil pads and such. Sorry, the name escapes me...

Vern
05-26-2011, 10:33 PM
4 mesh... do they work. Has there been any viable feedback on them?

jackie schmidt
05-26-2011, 10:39 PM
Anybody taken a good look at my tuners. The feature a rubber dampener, some call it a snubber.

I dare not mention that I was the first to use this, I do not want to get stomped on like I was in the thread on Tuners, but some very prominant shooters have now copied the concept.......jackie

Vern
05-26-2011, 10:54 PM
Yep seems I saw someone stomping someone else on the rimfire boards about noodles, and rubber washers or bushings.
Cuz dont let them knock you down. Sometimes multiple people think about the same thing at the same time but one makes it out first.
Telephone for example.

Boyd Allen
05-26-2011, 11:34 PM
The commercial product that was referred to in the previous post, is made by Sims Vibration Labratory. Here is a link to the product. http://www.limbsaver.com/2011/firearms/41.php
Back when they were first introduced, they were called Deresonators. After reading about the first ones, that had a 5/8" ID, I was curious enough to call the mfg. and suggest that they make one that had a larger ID, for varmint and target weight barrels. Some time later, they sent me two prototypes that have 3/4" IDs. The rubber is quite gummy and stretchy. I have stretched one of them over a tuner that measures 1.25". If you tap a free floated benchrest barrel, with a small wrench and compare the sound with the same barrel that has one of the Sims rubber doughnuts mounted, the difference is quite noticeable. In the latter case, it is a dull thud of rather short duration. These units are inexpensive and widely available. Midway carries them. If you look at the article, in the Guns of the Week section, about Joe Fredrich's Rimfire rifle, you will see that in addition to a rather weighty tuner, his barrel has one of the Sims units, a couple of inches in front of the stock. http://www.6mmbr.com/gunweek078.html I eventually found that mine worked best (on a 10.5# 6PPC) 2" back from the muzzle, just behind the tuner that Jackie gave me (pre rubber and brass model). I have no doubt that the combination, with a little adjustment, made the barrel shoot better. It was one that I had shot quit a lot before putting the tuner on it. Their combined weight was about 5 1/4 oz.

4Mesh
05-27-2011, 12:59 AM
Thanks Boyd, that's exactly what I was thinking of.


4 mesh... do they work. Has there been any viable feedback on them?
I won't make any claims as to "work" or "not work". I will guarantee you they do "something" and it is very easily visible on a 1K target. There is a significant change in POI. I'll allow others to speculate as to why that is but I have seen it.

Grouping... As Harold Vaughn probably would have said, there is clearly a change, but isolating the group size portion of it in so many other variables is very difficult.

If it made things better, it was slight, but there wasn't a lot of room for improvement. It didn't make anything worse, and I'm pretty sure that would have been obvious.

JohnsonGunsmith
05-27-2011, 02:01 PM
4 Mesh
No programming experience at all.
No electronics experience.
This does interest me enough to learn how to make this all work.
I do not know what the learning curve will be but I am smart enough to figure things out and have always been pretty curious as to how things work from childhood.
I do not think you are implying this is impossible or even unlikely. I think you are saying the opposite that it is possible and that I should try it if I will commit to it and am willing to learn.
I will quickly spend $400 to see if there is the possibility of success.
as for the tools I only own the last 3 in the list. Mill, lathe and drill press. as far as being computer savvy I can do only the typical stuff most people do. When I have a problem I usually call a friend but I know a guy who is pretty good with computers. I have a finite amount of time as I am sure most people do and I would like to make up for some time by spending a bit extra but I am not afraid of work and am willing to do this on a budget in order to get some testing completed.
Thanks for all your help
Brandon J.

dennisinaz
05-27-2011, 03:51 PM
Can you dampen vibrations by using a very THICK heavy rubber bushing placed and moved up and down the barrel?
I have wanted to try this in the same manner as a tuner.
I know you can find the sweet/dead spot by tapping on a barrel and listening to it.


I have a Rem Mtn rifle that I had blue-printed by one of the big-name accuracy gunsmiths as an experiment to see exactly what would be gained over a stock rifle. I had a Krieger barrel installed with a fairly tight reamer. My accuracy was still nothing too interesting, even after a second barrel was installed (Hart first, then Krieger-which shot much better than Hart).

On a whim, I put a Limb-Saver barrel De-Resonator on it and slid it up to within a few mm of the forend. This actually made a noticeable difference. It is on very tight, doesn't move even in brush and makes it possible to shoot several weights of bullets to similar points of impact. Although I got mine free at the SHOT as a demo, they only cost about $10 and are worth playing with. They look a little dorky, but seem to be of some real value; at least on a thin barrel contour like this.

4Mesh
05-27-2011, 04:25 PM
Wonderful. Yes you are correct, I am not saying it is impossible, it is quite possible. And with some time, you WILL learn stuff about what happens to that gun when it goes bang, even if everything goes wrong.

You have the mill / lathe and drill press. You're in business. This other stuff is cheap.

Ok, 8 years ago I would have said that programming would have been easier to learn back in the 70's or 80's on something no longer available to buy. That has changed, and now I would absolutely advocate that little gizmo I posted the link to. Not only will it be so damn much fun you won't believe it, but it's as easy and as straightforward as programming is going to get. And, it doesn't cost an arm and a leg. I recommend that device since it has good resale value, and allows you a learning and debugging experience that you will never get on a PC. Any more, PC's suck for learning to do programming. At the beginner level anyway. It isn't that programming is difficult, but, nothing today is documented AT ALL, and you are google searching all the time to find every tidbit of information. That company there produces datasheets just like the old days. Yes, that datasheet for the processor thats included on the board is 1000 pages. But the info is in there. You don't need to find some obscure website to get info. And it's not like you need to read every single page and every word. You need to know the basics of each section that pertain to you, and you need deeper information when things don't work as expected. But the info is there, and its easy to find.

Your accelerometer is just one way to collect data. But like almost all methods, it's an analog device. Meaning, it will give you voltages between 0-5Vdc as a result. You need to catch those really fast, and you need to catch them as a number (Analog to Digital Conversion ADC). An oscilloscope is the easiest way. However, in some cases, it is not the best way. It sure is nice to have a scope for all the work on the circuits, and it doesn't have to be the fastest thing in the world. But when I did this, I did not collect usable data nearly as well with a scope as I did with a processor. I also didn't use an accelerometer, though I'd probably use a few now if I was to do it over again. I made my own devices. Be that as it may, you'll need to try all ways before it's all over. That 18Fxxx chip on those boards I linked has A-D converters on it. You simply set them up and read the values from ram. Easy as pie. The controller I'm working on right now will do 5 at one time, and sample them >1,000,000 times a second. For a small controller, that's unheard of. My chips were <$5 each. Fyi, I have no use for the A-D on them. It just happens to come with it, as it does many other things. That same chip is sold with more pins and will sample 9 simultaneous A-D's. at that speed, you would be able to have 4 2-axis samples simultaneously (4 sets of sensors on the barrel at the same time), and with a typical bullet ride of 2ms, lets say conservatively you could sample those 2400 times while the bullet is in the barrel. So, a super fast scope really not only isn't necessary, but, isn't going to give you this level of data collection cause this data you can actually get out of the chip and save, then move to excel or a database if you wanted to.

I would be willing to point you in the right directions (or what I think are right) but I will not do the work for you and will tell you that up front. I don't have time to invest. But I'd be happy to offer ideas as time permits. And I can give you shopping ideas that'll really help keep the cost down and fun factor up. Fun being what this is all about anyhow!

As long as you don't get discouraged, you'll find this a great experience. There's various forums full of folks who'll help with about any problem.

In the interest of not starting some flame war, I'd suggest we move this from the forum to email. Mines in my profile I think...

A scope will have a limited number of inputs. One of your inputs will be used just to tell the thing when to catch data. That is one limitation. Scopes with 4 channels or more are expensive. Scopes >100Mhz start to get expensive too. This is why your buddy said it would be an expensive undertaking. You don't need a super expensive scope, and that is why I say get a used one cheap. It might not have todays features, but people have built some pretty kewl stuff with scopes of 20 years ago. Many can be had because they are no longer young enough to be certified. They are essentially scrap to the company that is using them where they need certification with paper to back it up. It has nothing to do with them not working, it just means that nobody will stake their life that the numbers from it are dead on correct.

If you go to microchip.com, you can go TODAY and download FOR FREE, Mplab8.70. That software will allow you to simulate any processor they make, and actually run the code and sample apps, as well as pretend there is actually a device there connected to sensors and all sorts of crap, all within an integrated development environment (IDE - Program for making programs let's say). You can do that for $0.00 tonight. The new IDE is under development and that is what I use right now. I'm working on a project at the moment using a brand new type of processor (to me, not that old to anyone else really) and using the new IDE in its current Pre-release state and I love it. It will not simulate like the old Mplab will though. And for that 18F chip, it may be easier to begin with what already works.

I'll tell you this as incentive. I have personally gotten about a half dozen people started in micro-controller apps, all of whom have had virtually 0 prior experience with the stuff. Each has gone on to do projects of their own with 0 help from me or anyone else, and the stuff has worked for what they do. People from all age categories 15-60, but all folks like yourself who will stick their nose to the grindstone and learn the stuff.

Begin by making an LED flash on that board. From there, you'd be surprised how close you are to reading movement of barrels.

4Mesh
05-27-2011, 04:39 PM
I should also mention that as of last year, C Compilers for those chips (lite licenses) are available for free and that means you can now program those chips in the exact same language you use for programming your PC. And the compilers for your PC are free too. Now, this is NOT Basic, so, it's not 'quite' as simple as that. But is is fast, and basic is certainly not fast. C is fast... fast fast...

Don
05-28-2011, 08:46 PM
That sounds more like it. I do not have any of the equipment yet. I do not know why it would cost so much either but I was really discouraged after talking with him. I do not know what I am doing at all and am learning what I need as I go. Some of the things you said to me in the last post was over my head but I do understand the don't chicken out part and If I can do it for under $3000 I would be very intrested. Can you send me info. to get to the correct websites and places to get what I need? I am intrested and want to do some testing. I will be posting results on here after testing if it gets off the ground.
Thanks for the positive feedback and I feel like it is a possibility again.
Brandon J.

Hi Brandon,

4mesh is correct, putting together the equipment for good firearm vibrational analysis can be done for well under $2,000..................but requires a particular skill set readily proficient in electronics, mechanical vibration analysis, experiment developement and analysis, advanced firearm functioning, etc..

The few people that I know that are capable of providing assistance are somewhat reluctant to do so due to the complexity of the subject matter and the commitment that it takes to follow thru......................simply put, most individuals lose interest in face of the amount of effort that would be required.

My suggestion would be to duplicate some of Vaughns' equipment/experiments first; simple band pass filters, integrators, and accelerometers, and procure an inexpensive oscilliscope, then mirror some of Vaughns' experiments. This will be a good first step in seeing just how far you want to take this and provide an entry level of experience to learn the language, equipment, and scope of the task at hand in order to take the next step, all for less than $500.

Once you have acquired this basic level of knowledge and proficiency you will be able ask specific questions about equipment upgrades and vibration analysis that can be answered on these messageboards..................Don

Joe Salt
05-29-2011, 08:29 AM
I have Deresanators the full lenght of my heavy gun, that is were 4Mesh seen them. They work on that rifle, I've won a lot of score matches in the wind with it, I call it my wind gun. Tried them on my wife rifle,but did not see an improvement in accuracy because the rifle shot so well to begin with. I belive some are vibration sensitive some are not,you're only going to tweak so much out of a good shooting rifle or barrel. Now the bad one's you can improve.

Joe Salt

frwillia
05-29-2011, 11:12 AM
Reading to catch up on this thread a quote from one of my engineering co-workers drifted through my head and caused me to chuckle a bit - so thought I'd share it:

"Everybody believes an analysis, except the guy that did it. Nobody believes a test, except the guy that did it."

Fitch

mikecr
05-29-2011, 11:40 AM
I tried to passively capture muzzle movement on a 16.5lb br gun off a rest(1st attempt -FAIL).
This was using a laser mic, modified Oehler optical sensor, DAS, software/Laptop, precision mounting, etc(several $thou, nicely built FAILURE).
Some things learned so far:
1. Recoil invalidates everything
2. However fast & fine your resolution -AIN'T ENOUGH
3. This will not be cheap

It might not even relate to your endeavor. Just throwin in what I can.

4Mesh
05-29-2011, 02:23 PM
"Everybody believes an analysis, except the guy that did it. Nobody believes a test, except the guy that did it."

Fitch
That's pretty profound, good one.

Having always believed that anyone can do anything, I came up with a saying for nay-sayers long ago that goes like this.

Prit near everyone I ever saw who does something, when they did it for the first time, they'd never done it before.

In other words, people have no divine grace. If they can learn it, so can anyone else. Experience is obtained by getting experience. You also don't need to have someone spoon feed you data in order to learn something. The first person to discover anything did so without being shown by someone else, and so can you. School is not about learning, it's about learning how to learn.

Mikecr, did you give up after that? Had you considered that the data you wanted was in what you collected, but just wasn't obvious? Mhz isn't enough resolution? How fast do you think a barrel can vibrate mechanically? I agree, recoil's a bitch. But, you might also consider that vibrations are predictable to a degree, so you don't need to take the reading while it's recoiling... You can back into what it used to be (if you want to)

mikecr
05-29-2011, 07:22 PM
I agree, recoil's a bitch. But, you might also consider that vibrations are predictable to a degree, so you don't need to take the reading while it's recoiling... You can back into what it used to be (if you want to)

Viewing(like with an oscope) should be easy, but recording is tougher. I just revisited my DAS and see that it's not as high in recording speed as I had thought. It samples at 14Kb/sec, which only provides 1.1K samples(defined) per second and a USB throughput into my spreadsheet table at only 240hz. Way too slow..
I could upgrade to 4.8K samples/sec capture software for ~$200 (keeping same hardware). But I don't know yet if that would be fast enough. I also need to point my laser mic at a dremel and watch it's output with a scope. Maybe it's not quick enough, and maybe it's 1thou resolution don't get it.

My objective was to record muzzle movement and position at bullet release. I wanted to see the differences between tuned and out of tune, and really only expected to 'see' where the muzzle was pointed -in only the vertical axis. I didn't foresee this all being so fast though.
Given the recoil, and in hindsight, my passive measure may not be a sound approach.
The field barrel doesn't just move up/down, but backward and side to side.
And lacking the resolution needed anyway, all I saw was some crazy recoil itself.
With better resolution, I will still need to subtract or normalize this recoil in my graphs..

It was ~6mos ago when I tried it, and I haven't gone back to it since(busy elsewhere).
I'll go at it again before the year's out, so I'm very intersted in this discussion.

Don
05-29-2011, 07:35 PM
Here is a relatively inexpensive "Vibrations for Dummies" universal laboratory kit (complete reference and support information data included) for around $180 and along with a $300 multi channel oscilliscope will get an individual well into the analysis of gun barrel vibrations, without having to build alot of the sensors, circuits, accelerometers, and other components that Vaughn had to develope in his efforts.............Don

see pg. 22/23 "Vibrations/Accelerometer design kit"


http://apps.meas-spec.com/myMeas/MEAS_download/Catalogs/Piezo/Piezo_Product_Guide.pdf


http://parts.digikey.com/1/parts/955190-sensor-piezo-film-design-kit-0-1004308-0.html

Vern
05-29-2011, 08:36 PM
Mike I want to try and ask this in such a way so as not to allow the thread to be hijacked.
There have been several threads in the past where recoil, time and distance was discussed.
However I never once saw anything other than math for answers. For a basic lets say ppc or pick any other caliber.
1. How much time elapses from primer ignition and the bullet leaving an average barrel.
2. How much has the gun moved in a rearward direction due to recoil before the bullet leaves the barrel.
Rather than everyone start throwing in "depends on the variations, caliber etc etc.
Give me some kind of generalized answer..... appprooooox ? milisecs approooooxxxxx 1/4" recoil,,,2" recoil just some small idea is all I ask.
Thanks

Don
05-29-2011, 09:37 PM
Mike I want to try and ask this in such a way so as not to allow the thread to be hijacked.
There have been several threads in the past where recoil, time and distance was discussed.
However I never once saw anything other than math for answers. For a basic lets say ppc or pick any other caliber.
1. How much time elapses from primer ignition and the bullet leaving an average barrel.
2. How much has the gun moved in a rearward direction due to recoil before the bullet leaves the barrel.
Rather than everyone start throwing in "depends on the variations, caliber etc etc.
Give me some kind of generalized answer..... appprooooox ? milisecs approooooxxxxx 1/4" recoil,,,2" recoil just some small idea is all I ask.
Thanks

1.2 milliseconds

.135"

Vern
05-29-2011, 09:39 PM
Don thank you so very much.
I will start a new thread and have some more relevant questions for this one. But alas it will have to be tomorrow.

4Mesh
05-30-2011, 12:50 AM
Vern,

As you'd figure, the numbers vary by what rifle..

using numbers from a 30 Cal WSM 16.5# light gun with a 210 bullet at 2850fps, the numbers would be around .050" and closer to 2ms duration.

Mike, yes, it sounds like you were seriously handicapped with the speed at which you took the measurements. Again, that's sorta why I say a scope isn't always best for catching that stuff. It happens I have a pretty nice one. 8 channels @ 1.5Ghz, storage pre, post, whatever. Trouble with that is, A, I don't really like taking it outside. B, it is very temp sensitive so it spends all it's time re-calibrating if it sees the sun, C, exporting converted values ain't its strength. Truth be told, the input devices don't have bandwidth of that level anyhow so catching extra values is kidding myself. So, it goes back to using a controller to catch the numbers, and they are getting faster by the day. I looked up the datasheet on the chip I linked above on that proto-board and it runs at 64Mhz (16mips), has 13 A-D converters. It's probably capable of 20x the real resolution you were seeing, and again, there are much better choices still. For catching a lot of data, a super fast microcontroller is a better choice. Yes, they are a LOT more work than hooking up a probe, but, you get usable data.

mks
05-31-2011, 12:02 PM
Mike I want to try and ask this in such a way so as not to allow the thread to be hijacked.
There have been several threads in the past where recoil, time and distance was discussed.
However I never once saw anything other than math for answers. For a basic lets say ppc or pick any other caliber.
1. How much time elapses from primer ignition and the bullet leaving an average barrel.
2. How much has the gun moved in a rearward direction due to recoil before the bullet leaves the barrel.
Rather than everyone start throwing in "depends on the variations, caliber etc etc.
Give me some kind of generalized answer..... appprooooox ? milisecs approooooxxxxx 1/4" recoil,,,2" recoil just some small idea is all I ask.
Thanks

These are some of the right questions to ask before a system can be designed for studying barrel motion. Here are some other important criteria:

1. Since the time the bullet spends in the barrel is roughly a millisecond, the sampling rate of the data acquisition system must be much faster, say 1 MHz.

2. During that millisecond, the rifle travels rearward about 0.1", while the muzzle moves vertically a few thousandths. Since we are most interested in controlling vertical motion to tune a rifle, we need some measurement mechanism that can focus on the small vertical measurement, in spite of the much larger horizontal recoil motion.

3. The vertical position of the muzzle has little influence on where the bullet strikes the target. What is most important is muzzle angle. One inch difference in elevation at a 100 yard target results from a less than 0.02 degree change in muzzle angle. Therefore, we need to measure the angle with greater accuracy, say +/- 0.0001 degree. Or if we approximated the angle by measuring two points separated by an inch near the muzzle, the difference in the heights of the two points would be less than 0.0003". Therefore, we would need to measure the two heights with accuracy much greater than 0.0003", say millionths of an inch.

Meeting criterion 1 is not a problem, there are plenty of systems with high sampling rate.

Criterion 2 is more difficult. In a previous thread, I think it was Vibe who suggested that initial experiments be done with a rimfire rifle clamped to a huge bench, to eliminate recoil motion. While there could obviously be some differences in the response of such a gun and that of a more typical BR rifle, it would be a place to start.

Criterion 3 is probably the most difficult. Measuring millionths of an inch can be done under a microscope, or maybe by capacitance. Small angles might be measured by bouncing a laser off a mirror attached to the muzzle and measuring the displacement of the laser beam at some distance from the mirror with a high speed camera. The laser/camera system might be best because it measures angle directly, but a 1 MHz camera is probably in the $10k-100k range. Capacitance would likely be cheapest and could produce good results. Whichever system is chosen, it would need to be isolated from the vibration of the rifle.

Acceleration is not worth the effort IMHO. It just doesn't measure what is really important. Acceleration must be integrated twice to approximate displacement, which causes inaccuracy. And one would need two accelerometers to find muzzle angle, which would involve even more inaccuracy.

Cheers,
Keith

Vibe
05-31-2011, 12:29 PM
These are some of the right questions to ask before a system can be designed for studying barrel motion. Here are some other important criteria:

1. Since the time the bullet spends in the barrel is roughly a millisecond, the sampling rate of the data acquisition system must be much faster, say 1 MHz.

2. During that millisecond, the rifle travels rearward about 0.1", while the muzzle moves vertically a few thousandths. Since we are most interested in controlling vertical motion to tune a rifle, we need some measurement mechanism that can focus on the small vertical measurement, in spite of the much larger horizontal recoil motion.

3. The vertical position of the muzzle has little influence on where the bullet strikes the target. What is most important is muzzle angle. One inch difference in elevation at a 100 yard target results from a less than 0.02 degree change in muzzle angle. Therefore, we need to measure the angle with greater accuracy, say +/- 0.0001 degree. Or if we approximated the angle by measuring two points separated by an inch near the muzzle, the difference in the heights of the two points would be less than 0.0003". Therefore, we would need to measure the two heights with accuracy much greater than 0.0003", say millionths of an inch.

Criterion 3 is probably the most difficult. Measuring millionths of an inch can be done under a microscope, or maybe by capacitance. Small angles might be measured by bouncing a laser off a mirror attached to the muzzle and measuring the displacement of the laser beam at some distance from the mirror with a high speed camera. The laser/camera system might be best because it measures angle directly, but a 1 MHz camera is probably in the $10k-100k range. Capacitance would likely be cheapest and could produce good results. Whichever system is chosen, it would need to be isolated from the vibration of the rifle.

Cheers,
Keith

They are pricey, but Keyence makes such a device.

Fastest in the World: 392kHz sampling rate
Highest Accuracy in its Class: 0.02% of full scale (Full scale being as small as 1mm or 0.04")
Highest Repeatability in its Class: 0.005μm (.005 * .001mm = .000005mm = .0000002")


http://www.keyence.com/products/measure/laser/lkg5000/lkg5000.php?pb=LT.01.LK
http://www.keyence.com/products/measure/laser/lkg5000/lkg5000_specifications_1.php

4Mesh
05-31-2011, 05:00 PM
Vibe,


Their repeatability is down to very tight tolerance (i'm skeptical), but the accuracy is more in line with what most of us would believe. Something tells me they have the wrong suffix in the .005. Yes, they clearly say .005um, but I've been around non-contact measuring for a pretty long time and as a rule, it doesn't split things down quite like that. Maybe that's possible but, that seems a bit optimistic for that sort of device. The accuracy part is not hard to believe at .02%. The repeatability is a bit much to swallow, expecially with repeatability so high and accuracy so relatively low. Lasers are kewl and all but they're not magic. I mean, they graphic on the page shows it looking at a casting...

If they mean .005 Millimeters (more likely), that would still be .005m .25.4 = about .0002". This I could buy. It would not be the first time I saw specs listed with optimistically errant numbers.

Even still, that device seems like it would be easy enough to make with components at home. Remember in this application, you don't have to have the accuracy, it just needs to repeat.

PS. The same pic chip listed above has the timer/counters for that job too...

TRA
06-01-2011, 01:49 AM
That .005 is listed only for a measurement range of +/-.5mm.

Trying to isolate and measure only the barrel vibrations seems like an exercise in futility. It should keep you occupied.

alinwa
06-01-2011, 02:00 AM
I feel that one of the best ways to map barrel vibration/launch angle is to shoot over a good chronograph and map the sine wave on the target.

al

Don
06-01-2011, 02:57 AM
Acceleration is not worth the effort IMHO. It just doesn't measure what is really important. Acceleration must be integrated twice to approximate displacement, which causes inaccuracy. And one would need two accelerometers to find muzzle angle, which would involve even more inaccuracy.

Cheers,
Keith


Depends upon what you are trying to analyse, say if it were to distinguish between a .5 grain powder load difference in a gun I would agree, but if you were trying to distinguish the damping affect of a synthetic collar in a railgun block vs a metallic collar you would see the difference..................how do know? Ive observed it many times, much easier to distinguish large amplitude variations than slight frequency changes...............Don

JerrySharrett
06-01-2011, 06:20 AM
My suggestion would be to duplicate some of Vaughns' equipment/experiments
Once you have acquired this basic level of knowledge and proficiency you will be able ask specific questions about equipment upgrades and vibration analysis that can be answered on these messageboards..................Don

Hey DJ, if we could get Greg Walley at Kelblys interested.....He came from the electronics world and has done some complex electronic testing on the Kelbly trigger timing and a few other items. Besides, he has a great range just outside his door and a great shop just inside!!!!

4Mesh
06-01-2011, 10:33 AM
I feel that one of the best ways to map barrel vibration/launch angle is to shoot over a good chronograph and map the sine wave on the target.

alIf it were the biggest error component (by far) then I'd agree. But otherwise, there's too many other variables clouding the results. In other words, if that would work, then there's some really basic mechanicals troubles that need fixed first.

Roy Allain
06-01-2011, 01:44 PM
Here is a relatively inexpensive "Vibrations for Dummies" universal laboratory kit (complete reference and support information data included) for around $180 and along with a $300 multi channel oscilliscope will get an individual well into the analysis of gun barrel vibrations, without having to build alot of the sensors, circuits, accelerometers, and other components that Vaughn had to develope in his efforts.............Don

see pg. 22/23 "Vibrations/Accelerometer design kit"


http://apps.meas-spec.com/myMeas/MEAS_download/Catalogs/Piezo/Piezo_Product_Guide.pdf


http://parts.digikey.com/1/parts/955190-sensor-piezo-film-design-kit-0-1004308-0.html


Don, the first http doesn't work. Is there another way?

Roy

mks
06-01-2011, 01:51 PM
Depends upon what you are trying to analyse, say if it were to distinguish between a .5 grain powder load difference in a gun I would agree, but if you were trying to distinguish the damping affect of a synthetic collar in a railgun block vs a metallic collar you would see the difference..................how do know? Ive observed it many times, much easier to distinguish large amplitude variations than slight frequency changes...............Don

Don,
I'm not saying that acceleration is worthless, just not worth the effort. It is easy enough to glue an accelerometer to a barrel and get data. But the trouble is that the correlation between acceleration and barrel tune is not clear. It may seem intuitive that reducing acceleration would improve accuracy, but the opposite is more likely the case. From VarmitAl's simulations, we see that greater muzzle angular velocity (in the vertical plane) at the time of bullet exit is needed to compensate for variations in bullet exit time for all barrel contours tested. Further, increasing vertical acceleration doesn't necessarily mean that muzzle angular velocity at the time of bullet exit will increase.

Now transverse acceleration is another story. We want to eliminate all transverse muzzle motion. The correlation between transverse acceleration and transverse muzzle angular velocity is similarly imperfect, but is probably good enough if the goal is zero. The exception would be when the accelerometer is located on a node, in which case it would read zero regardless of the angular motion.

Cheers,
Keith

mks
06-01-2011, 01:57 PM
I feel that one of the best ways to map barrel vibration/launch angle is to shoot over a good chronograph and map the sine wave on the target.

al

Good point, Al. Throw in some intentional variations in powder charge/muzzle velocity, and this is probably the easiest, and arguably the most relevant, way of getting an indication of muzzle angle.

Boyd Allen
06-01-2011, 03:06 PM
At the risk of being pummeled, I think that we have sufficient information as to how the parts work, but the subtleties and unpredictability of all the various combinations' interactions may prevent useful prediction of outcome, and so, to a large extent, we are mostly left with cut and try. For example, I know of no barrel maker that claims that he can, by inspection, pick out a hummer barrel. Some things can be done "by the numbers" some cannot. We are like the weather man who says that it rained, and here is why it did. Things are a lot easier to explain than predict, and many times the explanations are no more than experienced guesses. Ya...I know; you knew all that.

Don
06-01-2011, 06:27 PM
Don, the first http doesn't work. Is there another way?

Roy

Roy, this should get you there, see last page of the pdf guide...........Don


http://www.meas-spec.com/downloads/Piezo_Film_Product_Guide.pdf

Greg Walley
06-01-2011, 08:00 PM
Hey DJ, if we could get Greg Walley at Kelblys interested.....He came from the electronics world and has done some complex electronic testing on the Kelbly trigger timing and a few other items. Besides, he has a great range just outside his door and a great shop just inside!!!!

Jerry,

I looked into barrel vibration measurement at one time...and it was Don Jackson that gave me some pointers on sensor selection and mounting. That was several years ago, and measurement technology has come a long way since then. There are very low mass devices that would probably work well for our application and the barrel tapers we use on BR rifles.

I never bothered with the project due to all of the work involved for obtaining data that probably won't be relevant to what we are looking for. However, as 4Mesh has pointed out - there are many new ways for cheap data acquisition as long as one has a modern laptop. There are some freeware programs that are user friendly. I did a lot of research and planning a few years ago on this topic, but unfortunately my hard drive crashed two weeks ago, so I don't have ready access to that information at this time.

I became more interested in measuring strain, but I was a little discouraged with finding a way to control for temperature with the sensors available at the time.

There was a paper published on measuring gun barrel vibration using fiber Bragg grating sensors coupled to a spectrum analyzer. I think it was published in Measurement Science Technology. I'll see if I saved this article elsewhere and post it here, since it had a lot of infomation pertaining to what we're looking for. If I recall correctly, the article addressed the complexity of temperature compensation. The above technique would be expensive, so basic analog I/O with standard strain and vibration sensors would be the way for the hobbiest.

It might be possible to use a freeware audio analysis program with FFT, like Steinberg Wavelab and read the sensors through the high impedence microphone inputs on the laptop soundcard, and do all of the filtering through the software.

Vern
06-01-2011, 08:15 PM
Serious question.....
why is it I only see for the most part vertical vibration addressed when there can be horizontal.

In that respect what about an elliptical tuner that could address that issue?

mks
06-01-2011, 09:25 PM
Serious question.....
why is it I only see for the most part vertical vibration addressed when there can be horizontal.

In that respect what about an elliptical tuner that could address that issue?

Vern,
Don't forget axial and torsional vibration, too. The reason vertical vibration is discussed most is because it is normally the largest component, and the only component that we want some of. All the rest we want to be zero. Vertical vibration is greater than horizontal vibration because bolt thrust is above the center of gravity of the rifle, but is nearly aligned with it side to side. Pure axial and torsional vibration don't contribute significantly to shot dispersion.

Keith

mks
06-01-2011, 09:30 PM
...I think that we have sufficient information as to how the parts work, but the subtleties and unpredictability of all the various combinations' interactions may prevent useful prediction of outcome...

Boyd,
I am flabbergasted by your logic. How can one not need more information on something that is currently unpredictable? Consider yourself pummeled.;)

Cheers,
Keith

David Merrill
06-01-2011, 09:52 PM
From the point of view of accurately measuring the other components of lateral barrel motion, don't forget that there is a dialational transient as the bullet and gas pressure pass the measurement location.

Also, there is a bit more to the effects of transverse barrel muzzle motion than simply the pointing direction of the muzzle at bullet exit. Again, research the meaning of 'muzzle jump' and 'aerodynamic jump'. Finally, don't lose track of the bottom line objective that it is the shot-to-shot consistency that contributes to target accuracy, not just the magnitude of the barrel motion.

David Merrill

Vibe
06-02-2011, 09:40 AM
Serious question.....
why is it I only see for the most part vertical vibration addressed when there can be horizontal.

In that respect what about an elliptical tuner that could address that issue?Vern,
Don't forget axial and torsional vibration, too. The reason vertical vibration is discussed most is because it is normally the largest component, and the only component that we want some of. All the rest we want to be zero. Vertical vibration is greater than horizontal vibration because bolt thrust is above the center of gravity of the rifle, but is nearly aligned with it side to side. Pure axial and torsional vibration don't contribute significantly to shot dispersion.

Keith
You guys are starting to hit upon one of the reasons I've been objecting to the "parallel node" theory and terminology. We have to get past that mental picture (or theoretical model) to start to understand that mass at the muzzle only has an impact on one aspect of barrel behavior, the distribution of that mass - IE centroid in relation to the muzzle and barrel stiffness affects other aspects, and the overall mass moment of inertia of the tuner itself would impact aspects not even being discussed yet, such as these issues that you bring up.

Boyd Allen
06-02-2011, 11:29 AM
If we imagine that a thing works a certain way, we only have a theory, until testing verifies it, and even if the result is an improvement in performance, there is a good chance that we may not totally understand the reason for the change, because in making the intended change, it is highly likely that we have changed something else, that we were not looking at. I love imagining how things work, with an eye on making them work better, but without the capability of building what we imagine, so that we can test as we go, all that we have is a pleasant, albeit harmless distraction. This is why my next goal is not a new rifle, but a lathe, so that I can build and test ideas....cut and try. It is hard to write this as I sit recovering from my recent pummeling, but I somehow manage to carry on, despite my injuries.;)
Boyd

mks
06-02-2011, 03:42 PM
Some interesting reading for you.

http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA162135

http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA201713

http://www.arl.army.mil/arlreports/2000/ARL-MR-492.pdf

http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA474853

http://www-personal.umich.edu/~cwkauff/Aero729/file/PRODASV3%20User.pdf

Note mentions of 'muzzle jump' and 'aerodynamic jump'.

David Merrill

Excellent resources for this topic. In the Bornstein, et al. 1988 report, they measure tank cannon muzzle angle with eddy current proximity sensors. At least six are needed, three each at two points near the muzzle. These also provide horizontal and vertical displacement information. It is remarkable how closely their figure 6 (11300) of muzzle slope matches VarmintAl's simulation results.


There is a comparison of eddy current and capacitive sensors at http://www.lionprecision.com/products.html. In general, capacitive has higher resolution, but lower frequency response. Either could work well enough. Price is not listed.

4Mesh
06-02-2011, 05:00 PM
For almost 100 years, there was an idea about how bullets were blown by the wind that was universally accepted as fact. Documented in books, accepted by the Military, by ballisticians, etc. After further investigation, it was shown not to be fact. Now it is accepted that drag causes the effects.

With barrel vibrations, a whole lot of this is voodoo to most of us. Even those who've got a pretty good grasp on things are reluctant to just start blirting out answers. This is a little more complex than measuring the diameter of a bullet. What that means to most of us is that there's going to be fewer people working on finding the facts, and that there's going to be a good deal of disagreement on them once they're found. That doesn't mean people should not look. And it does not mean that a person has to account for all things in order for their findings to mean something.

The troubles with this particular research are several. It requires effort in several different fields to mean anything. It is not the sort of thing that sharing information is a big help, so, it does not lend itself well to cooperation. That's probably the biggest issue. Besides that, a person has to have a machine shop and be willing to delve into electronics a bit, not a common combination. Last but not least, we may be looking for a problem that doesn't exist. The real testing should be done by taking a 0 shooting gun, and making it worse.

Vern
06-02-2011, 05:53 PM
The reason for so many of the questions I am asking especially concerning vibration other than vertical is the possibility of an elliptical tuner. I have an idea but before I go to the expense of trying it I want to know if there is anything to warrant it or is it all in my imagination.
I wish Jonathan could get video like he was talking about and that would solve a lot of it..

But then again if we really start finding out all of the secrets that really make a difference then the sport wont be so much fun just trying to figure it out.

frwillia
06-02-2011, 07:56 PM
If we imagine that a thing works a certain way, we only have a theory, until testing verifies it, and even if the result is an improvement in performance, there is a good chance that we may not totally understand the reason for the change, because in making the intended change, it is highly likely that we have changed something else, that we were not looking at. I love imagining how things work, with an eye on making them work better, but without the capability of building what we imagine, so that we can test as we go, all that we have is a pleasant, albeit harmless distraction. This is why my next goal is not a new rifle, but a lathe, so that I can build and test ideas....cut and try.

Awesome! You are going to have some serious fun! You will soon wonder how you ever managed to get this far in life with out a lathe.

Fitch

alinwa
06-03-2011, 02:17 AM
.................. This is why my next goal is not a new rifle, but a lathe, so that I can build and test ideas....cut and try.

Boyd


Dude!! Really???

Manalive I hope it works out...... lathes is fun ;)

al

mks
09-03-2011, 01:32 PM
Varmint Al posted this link on the rimfire board:

http://www.border-barrels.com/articles/rimfire_accuracy/tuning_a_barrel.htm

Border Barrels used polarizers to measure muzzle angle. Wish I had thought of that. The linked article explains why we want rising muzzle angle very clearly, and shows an example of how a tuner accomplishes this. Highly recommended reading.

Cheers,
Keith

alinwa
09-03-2011, 01:36 PM
linkie no workie

Charles E
09-03-2011, 03:26 PM
linkie no workie

Geee, it workie for me-ee. (Windows Vista, Firefox).

Boyd Allen
09-03-2011, 03:49 PM
Me too. (XP, Firefox)

alinwa
09-03-2011, 04:35 PM
Worked fine w/Google Chrome.... great article!

al

David Merrill
09-03-2011, 08:11 PM
Some of you might be interested in these folks:

http://www.prodas.com/

http://www.google.com/#sclient=psy&hl=en&source=hp&q=%22arrow+tech%22+prodas&pbx=1&oq=%22arrow+tech%22+prodas&aq=f&aqi=g1&aql=&gs_sm=e&gs_upl=14328l17629l0l18095l7l7l0l0l0l0l186l894l1.6 l7l0&bav=on.2,or.r_gc.r_pw.&fp=85119c93305b22d6&biw=1316&bih=1066

David Merrill

alinwa
09-03-2011, 11:24 PM
Some, myself included, disagree with the verity of this statement "However, it is the pressures generated by the burning primer and powder that gives rise to the barrel vibrations."

I believe that a large portion of the overriding vertical component is generated by the use of a mechanical firing pin.

al

Boyd Allen
09-04-2011, 12:07 AM
Al,
Why would the pin favor the vertical over the horizontal.
Did Vaughn come to this conclusion?
Boyd

alinwa
09-04-2011, 01:15 AM
It's not the pin itself, it's the fact that the mechanism holding the pin back puts a vertical tension into the system.

I think this overriding vertical component is necessary for tuning, I've heard that electrically ignited systems, "stretchers" and even barrel blocked systems which often produce round groups through a wide velocity range can be nearly immune to "tuning" techniques.

For myself I've only played with blocking and bedding but I spend my life "making the rifle produce good clean vertical" and then "tuning it out." If I can't make a rifle produce vertical I'm lost.

round groups suck, unless they're dots.

Vaughn didn't get into this in 'Rifle Accuracy Facts'

unsupportedopinionsby





al

mks
09-04-2011, 11:06 AM
Some, myself included, disagree with the verity of this statement "However, it is the pressures generated by the burning primer and powder that gives rise to the barrel vibrations."

I believe that a large portion of the overriding vertical component is generated by the use of a mechanical firing pin.

al

Firing pin force is 20-25 lbs. Bolt thrust due to 60k psi peak chamber pressure on a .473" diameter case rim (0.176 square inches) is 10,500 lbs, over 400 times larger. I can't see how the small firing pin force can cause more vertical than the much larger powder burn force.

Although I don't agree with his calculation method, Vaughn on page 67 estimates the dispersion due to variation in firing pin force to be no more than 0.007-0.010" and concludes that "firing pin impact is not a significant contributor to dispersion."

If firing pin impact were the most important cause of vertical vibration, then one would expect a Remington Etronx rifle to have less muzzle jump on recoil. My 243 Etronx has as much muzzle jump as one would expect from a rifle with a mechanical firing mechanism. It also shoots groups that have about the same vertical as the average Rem 700.

Cheers,
Keith

David Merrill
09-04-2011, 11:25 AM
Some more interesting reading:

http://www.prodas.com/XQ/ASP/P.603/QX/webPageXML4.htm

David Merrill

alinwa
09-04-2011, 12:22 PM
Firing pin force is 20-25 lbs. Bolt thrust due to 60k psi peak chamber pressure on a .473" diameter case rim (0.176 square inches) is 10,500 lbs, over 400 times larger. I can't see how the small firing pin force can cause more vertical than the much larger powder burn force.

Although I don't agree with his calculation method, Vaughn on page 67 estimates the dispersion due to variation in firing pin force to be no more than 0.007-0.010" and concludes that "firing pin impact is not a significant contributor to dispersion."

If firing pin impact were the most important cause of vertical vibration, then one would expect a Remington Etronx rifle to have less muzzle jump on recoil. My 243 Etronx has as much muzzle jump as one would expect from a rifle with a mechanical firing mechanism. It also shoots groups that have about the same vertical as the average Rem 700.

Cheers,
Keith

keith,

It's not about relative force. It's not about firing pin impact. As I said, Harold didn't talk about it in the book.

Remington Etronix setups shoot round groups..... BIG round groups.

al

David Merrill
09-04-2011, 01:40 PM
And some more:

http://www.dtic.mil/ndia/2009infantrysmallarms/tuesdaysessioniiisiewert.pdf

http://www.dtic.mil/ndia/2006smallarms/weinacht.pdf

http://en.wikipedia.org/wiki/External_ballistics

David Merrill

mks
09-04-2011, 09:55 PM
keith,

It's not about relative force. It's not about firing pin impact.

al

Please explain.

Thanks,
Keith

alinwa
09-05-2011, 01:30 PM
Please explain.

Thanks,
Keith

Due to the angled sear engagement surfaces forces, the cocked system is not only biased upward but actually bent. The situation has been recognized for years and system mods like 'Borden Bumps' and parallel engagement surfaces, bolt lug/boltface modifications and trigger timing address it.

The major vertical drivers associated with the firing impulse are barrel droop and assymetrical bending from recoil lug flexure. And its associated flexure of the stock...

I believe that eliminating or mitigating certain of these vertical components leads to an un-tunable system.

al

frwillia
09-06-2011, 11:39 AM
Due to the angled sear engagement surfaces forces, the cocked system is not only biased upward but actually bent. The situation has been recognized for years and system mods like 'Borden Bumps' and parallel engagement surfaces, bolt lug/boltface modifications and trigger timing address it.

The major vertical drivers associated with the firing impulse are barrel droop and assymetrical bending from recoil lug flexure. And its associated flexure of the stock...

I believe that eliminating or mitigating certain of these vertical components leads to an un-tunable system.

al

Hypothetically, if all the vertical components are eliminated, which doesn't seem likely, I'd think the system wouldn't need tuning.

Fitch

Boyd Allen
09-06-2011, 06:19 PM
Al,
Exactly what bends? As far as I am aware, the bolt raises until stopped by the underside of the rear bridge, and in the process the lug engagement is reduced to a line at the end of the bottom lug. As soon as the trigger releases the cocking piece the bolt starts to fall. If the case is fire formed and shoulder setback from sizing minimal, this acts as a limit as to how far the lugs can be angled off of their seats. The current 200 yd.record for a sporter class short range benchrest rifle, is .086 (Tom Libby). This was shot with an action that has no Borden bumps. It is one thing to guess about limiting factors, it is another to accurately assign magnitude of importance. If there is a design flaw, it should cause a problem all the time. Last Saturday, a friend broke a range record at Visalia, shooting a .105 at 200 with a 10 1/2 # rifle, a plain old, angled interface, Panda. Modern equipment has a lot a potential, and if one is not seeing these sort of results, and the bolt fit is benchrest typical, I would look somewhere else for the problem.
Boyd
Boyd

alinwa
09-06-2011, 08:04 PM
It's not a design flaw, it's a good design. It's proven to work. It HAS an overriding vertical component which Libby used to tune his rifle to perfection.


"I believe that eliminating or mitigating certain of these vertical components leads to an un-tunable system."

That's me in the quote, from this thread........ ummm, yeahhh, Libby's gun works.... it's all good.....

Nobody is hearing what I'm saying, so I'll stop.

al

mks
09-06-2011, 09:49 PM
Hypothetically, if all the vertical components are eliminated, which doesn't seem likely, I'd think the system wouldn't need tuning.

Fitch

No, you need vertical in the system to compensate for the unavoidable vertical caused by variation in muzzle velocity within a group. This is a very important concept that is nicely explained in the Border Barrels link.

Cheers,
Keith

mks
09-06-2011, 10:13 PM
"I believe that eliminating or mitigating certain of these vertical components leads to an un-tunable system."


Now this I can agree with. But the vertical from the cocking piece, barrel droop, recoil lug and stock are all driven by and/or secondary to (and smaller than) the moment created by the force of the chamber pressure above the center of gravity of the typical BR rifle. 10,500 lbs bolt thrust times 1-2 inches moment arm equals 875-1750 ft lbs of torque. (Good thing it only lasts for a millisecond or so.) We need that torque to whip the barrel upward to have a chance for tuning. Now lower the boreline to the CG and it is a different story. The other effects you mentioned could still be active, but in my opinion, would have little chance of being able to accomplish tuning because they are so much smaller.

Cheers,
Keith

Boyd Allen
09-06-2011, 10:29 PM
Al, I read you. My question referred to this."the cocked system is not only biased upward but actually bent." BTW how does trigger timing come into this?
Boyd

alinwa
09-06-2011, 11:45 PM
Al, I read you. My question referred to this."the cocked system is not only biased upward but actually bent." BTW how does trigger timing come into this?
Boyd

The "trigger timing" you're referring to has to do with where in the cocking stroke the sear picks up. This timing as ref'd by Jim Borden or Jerry Stiller, or yourself, is different than the timing referred to by Bill Calfee in his "just relax" articles. Bill contends (and I don't disagree) that one way to skin the vibrational cat is to time the system to where the bolt is floating dead center (both lugs seated) when the pressure hits.

al

alinwa
09-06-2011, 11:57 PM
Now this I can agree with. But the vertical from the cocking piece, barrel droop, recoil lug and stock are all driven by and/or secondary to (and smaller than) the moment created by the force of the chamber pressure above the center of gravity of the typical BR rifle. 10,500 lbs bolt thrust times 1-2 inches moment arm equals 875-1750 ft lbs of torque. (Good thing it only lasts for a millisecond or so.) We need that torque to whip the barrel upward to have a chance for tuning. Now lower the boreline to the CG and it is a different story. The other effects you mentioned could still be active, but in my opinion, would have little chance of being able to accomplish tuning because they are so much smaller.

Cheers,
Keith

So why do electronically initiated rifles shoot round sloppy groups?

(pretend for a moment that you've heard they do..... ;) )


BTW, IME railguns set to below cg of the tracking system still 'tune.' Many high cg setups have been tried. In fact it's not at all hard to bed conventional stocks with enough upward bias that they recoil downward. Or redistribute parts. Shucks.... I put a big ol' hawg Schmidt and Bender on tall mounts above a Stiller action in a light stock a while back........ you stick a 3lb scope 2-1/2 inches above the bore....


BTW, why do you use the term "bolt thrust?" I've fired many rounds which exhibit zero actual bolt thrust, the head of the case doesn't even touch the boltface on firing.

al

Boyd Allen
09-07-2011, 12:12 AM
Al,
I know what trigger timing is. How does it come into what is being discussed, and again what bends?
Boyd

alinwa
09-07-2011, 02:08 AM
Boyd, trigger timing as you're referring to it affects the cycle because moving the pickup point fore and aft changes where the bolt is (how far it's dropped) when the rifle fires. Trigger timing be it Borden style or Calfee style affects bolt slap. IMO bolt slap is a major player in the generation of vertical vibration.

IMO the receiver bends.

IMO the receiver bends from upward pressure exerted by the angled cocking piece engagement. Is it meaningful??? I dunno. In the interest of science I did just go down and run a lever indicator on a couple receivers. Very crude, very jerry rigged but I did do it.

I stuck a mag base on the front rec ring, stylus bearing on the rear,

And I stuck a mag base on the rear, stylus bearing on the front.

And I stuck a mag base on the barrel, stylus bearing on the rear.

I waggled the rear of the receiver up and down with my fingers.

I inserted the bolt and carefully cocked the action in each of these situations.

I did this with an open bottomed 700 and with an XP100. The 700 is Borden Bumped which greatly lengthens the lever arm. The rear rec ring on the XP is short so I had to build a standoff.

In my test I did find repeatable deflection, I would call it a tenth on the XP and a half thou on the 700.

Was my test flawed? Yes.

But in my opinion it it did show deflection. And that the deflection produced by the tension in the system is 'similar' to the deflection produced by waggling with fingers.


A waste of time? Probably..... useful??? Probably not....


But I'm just sharing my opinion :)


al

frwillia
09-07-2011, 10:48 AM
No, you need vertical in the system to compensate for the unavoidable vertical caused by variation in muzzle velocity within a group. This is a very important concept that is nicely explained in the Border Barrels link.

Cheers,
Keith

Good point. I was thinking in terms of perfect ammo. Using what would otherwise be considered a flaw in the gun design to tune for flaws in the ammo is exactly what the article is talking about. Some days I'm hard to help. :o

Fitch

mks
09-07-2011, 06:03 PM
So why do electronically initiated rifles shoot round sloppy groups?

(pretend for a moment that you've heard they do..... ;) )


BTW, IME railguns set to below cg of the tracking system still 'tune.' Many high cg setups have been tried. In fact it's not at all hard to bed conventional stocks with enough upward bias that they recoil downward. Or redistribute parts. Shucks.... I put a big ol' hawg Schmidt and Bender on tall mounts above a Stiller action in a light stock a while back........ you stick a 3lb scope 2-1/2 inches above the bore....



BTW, why do you use the term "bolt thrust?" I've fired many rounds which exhibit zero actual bolt thrust, the head of the case doesn't even touch the boltface on firing.

al


Al,
Actually, the first 3-shot group from my 243 Etronx was a half incher at 100 yards. It won't always repeat this, but it doesn't seem any worse than other factory guns. From a barrel vibration standpoint, I wouldn't expect the lack of a firing pin spring to make a big difference, and in my limited experience it hasn't.

In principle, high CG guns can be tuned the same as low CG guns. Just need to time barrel exit to rising muzzle angle, whether it is on the first cycle or the second (or third, etc ...). In general this means that low CG guns need to be either considerably stiffer or considerably more flexible than tuned high CG guns to hit the right vibration cycle.

No overriding reason for "bolt thrust," just trying to use common terminology. The force gets transfered from the chamber to the rest of the gun regardless.

Cheers,
Keith

4Mesh
09-07-2011, 06:44 PM
Al,

I'd agree that maybe a Remington factory action would have measurable flex. Especially the ones with the bottom hardware (adl/bdl). But, for something like a 1.450" - 1.625" custom with no port in the bottom, theres not much flex. Boy, you better REALLY measure a while to find it if yer gonna look. But, guns built on those things can shoot vertical to beat all hell. So whats that say?

Maybe some rifles might have such a lock issue as to have measurable vertical due to what you suggest. But, I'd say it's a rare instance where that is the major contributor.

I'd say that unsprung weight, varying from above to below the bore line, is a much larger contributor to vertical. But still not the major ones when shooting long range. Those are on the reloading bench. imho... Should I have h in there? :D

Boyd Allen
09-07-2011, 07:25 PM
Al,
I have shot a cute little sporter that used caseless ammunition that was electronically ignited. The original .22 cal. bullets had been pulled and Bergers substituted. It was the ballistic equivalent of something on the order of a .222, or a little smaller. I was amazed at how well it shot, especially given the overall design. I would have not expected groups even half as good with conventional ammunition and ignition system.
http://guns.wikia.com/wiki/Voere_VEC-91
I suppose that if someone wanted to test the potential of electronic ignition in combination with more conventional, cased ammunition, he could find a supply of the primers as set to work using one of the discontinued Remingtons that have that feature. As with anything, reductions in what you refer to as bolt slap, reach a point of diminishing accuracy returns, and other factors become more important.
Boyd

alinwa
09-07-2011, 08:48 PM
Al,
Actually, the first 3-shot group from my 243 Etronx was a half incher at 100 yards. It won't always repeat this, but it doesn't seem any worse than other factory guns. From a barrel vibration standpoint, I wouldn't expect the lack of a firing pin spring to make a big difference, and in my limited experience it hasn't.

In principle, high CG guns can be tuned the same as low CG guns. Just need to time barrel exit to rising muzzle angle, whether it is on the first cycle or the second (or third, etc ...). In general this means that low CG guns need to be either considerably stiffer or considerably more flexible than tuned high CG guns to hit the right vibration cycle.

No overriding reason for "bolt thrust," just trying to use common terminology. The force gets transfered from the chamber to the rest of the gun regardless.

Cheers,
Keith

Keith,

1/2" guns aren't "tunable."

Boyd Allen
09-08-2011, 02:27 AM
Al,
Are you saying that 1/2" rifles do not show differences in accuracy depending on the specifications of their loads? It has been my experience that they do.
Boyd

alinwa
09-09-2011, 12:06 AM
Al,
Are you saying that 1/2" rifles do not show differences in accuracy depending on the specifications of their loads? It has been my experience that they do.
Boyd

no

Wildcatter
09-09-2011, 05:58 AM
Keith,

1/2" guns aren't "tunable."

I disagree completely with this statement. 1-1/2" rifles are tunable.... Hell, even shotguns are tunable.