SD and Barrel Harmonics

(((I use ES but that's just me, I think SD is a crutch)))

alinwa said:
This is probably a mistake, but I'm going to opine.

:)


IN MY OPINION, if one has to work up loads only at 100yds, then "SD" overrides anything "harmonic." (((I use ES but that's just me, I think SD is a crutch)))

IT IS MY OPINION that your statement above about "intuitively not correlated" is correct.

5 fps of velocity does equal near on an inch of vertical at 1000yds.

And (IMO) "harmonics" are used to OVERRIDE, or compensate for variations in velocity and are therefore yardage specific.

al
Click to expand...



I also agree.

When SD first appeared in reloading (probably back with the Oehler #33) it became the panacea, id est, "drug", of loading technique. While it does have some value, it is not the ultimate indicator that we would like it to be.

Most folks think that velocities should be as close to the same as possible, hopefully "0" ES. While that might not guarantee 0.000" groups, I doubt that anyone would suggest that larger ES's would be the right way to go. I mean offer me a ES of 4 fps or 40 fps, and I'll take the former every time.

But if we have a 3,500 fps load that gives a 10 round spread of +/- 4fps, it will (all other things being equal) produce a smaller 1,000 yd group, than a 10 round load that gives 9 rounds at 3,500, and one round at 3,480, even though the second group will have a smaller SD and a larger ES. In this case, the SD is NOT an indicator of a good load.

In a sense, as long as we measure groups by the furthest two holes, then the ultimate goal is to reduce the furthest two velocities... even though the SD will be a better tool to evaluate our loading technique.
 
Yes I like a small ES. but that is not the only part of the Equation. Just because you have a low ES. doesn't mean that is wear the gun is going to shoot the best, there have been other post that will tell you the bullet has to be a the right velocity for it to spin at the right RPM for it to become stable to buck the wind! That is what I look for, the right speed that everything comes together. So now when you change lot# of powder you can go back to that velocity. Or harmonics if thats what you want to call it.

Joe Salt
 
Good discussion

This has been a most interesting discussion with good input from some very knowledgeable individuals. I have read and re-read each post carefully and can clearly see there is still much confusion about one of my theories. :rolleyes:

If I'm not mistaken, I was the first to suggest that it's the column of air in the barrel being pushed out against atmospheric pressure that greatly affects the tune of our rifles. Take a couple of deep breaths, open your mind and listen carefully while I try to explain. Hope I can do a better job this time. :p

When I first made reference to the 'column of air in the barrel' it seems everyone zeroed in on the miniscule 'weight' of that air and completely overlooked the most important point I was trying to make and that is the weight of the earth's atmosphere and the fact that whatever is in the barrel must be pushed out ahead of the bullet against the weight of the atmosphere. Heavier air offers more resistance to bullet acceleration which affects bullet exit timing. If your rifle is perfectly in tune and the air thins due to an increase in temperature or drop in barometric pressure, bullets begin to exit the muzzle early.

The main thing that affects air density and hence rifle tune is change in temperature. Except for minor changes in barometric pressure, altitude at a given range doesn't change. The Midland Shooter's range is 2800 feet above sea level; that doesn't change, so the only thing to be concerned with is temperature. Yes, I know; some believe relative humidity is also critical but I assure you it is not. :rolleyes: Relative humidity goes up and down with changes in temperature even when there is no change whatsoever in the actual amount of moisture in the air.

I don't want to hijack this thread and if you guys want to discuss this in more detail, I can start a new one. What I'm trying to get across is important. I'm not crazy and know what I'm talking about but my communication skills leave a lot to be desired.

Gene Beggs
 
Gene all or skills in Communication is lacking! Yes I believe you're right about the air, but most of my loads are done at home before I leave for the range, so if thing change that much in temp. and pressure, my groups do suffer. So I have to try and find the best load all the way around. There are times when I have noticed a change in elevation, I always save my zero from match to match. So is this on the same line you are talking about? Cause when my zero doesn't change I shoot well.

Joe Salt
 
Re: Good discussion

Gene Beggs said:
This has been a most interesting discussion with good input from some very knowledgeable individuals. I have read and re-read each post carefully and can clearly see there is still much confusion about one of my theories. :rolleyes:

If I'm not mistaken, I was the first to suggest that it's the column of air in the barrel being pushed out against atmospheric pressure that greatly affects the tune of our rifles. Take a couple of deep breaths, open your mind and listen carefully while I try to explain. Hope I can do a better job this time. :p

When I first made reference to the 'column of air in the barrel' it seems everyone zeroed in on the miniscule 'weight' of that air and completely overlooked the most important point I was trying to make and that is the weight of the earth's atmosphere and the fact that whatever is in the barrel must be pushed out ahead of the bullet against the weight of the atmosphere. Heavier air offers more resistance to bullet acceleration which affects bullet exit timing. If your rifle is perfectly in tune and the air thins due to an increase in temperature or drop in barometric pressure, bullets begin to exit the muzzle early.

The main thing that affects air density and hence rifle tune is change in temperature. Except for minor changes in barometric pressure, altitude at a given range doesn't change. The Midland Shooter's range is 2800 feet above sea level; that doesn't change, so the only thing to be concerned with is temperature. Yes, I know; some believe relative humidity is also critical but I assure you it is not. :rolleyes: Relative humidity goes up and down with changes in temperature even when there is no change whatsoever in the actual amount of moisture in the air.

I don't want to hijack this thread and if you guys want to discuss this in more detail, I can start a new one. What I'm trying to get across is important. I'm not crazy and know what I'm talking about but my communication skills leave a lot to be desired.

Gene Beggs
Click to expand...

Good evening Gene.

Some theories are hard or impossible to prove or even document...

... but your is easy. Take a can of computer cleaner (often called "Dust-off" or "canned air"), which is a halogen-carbon gas, and fill the bore with it before shooting and see if there is a noticeable difference, either in measured velocity (I doubt it) or in group. It would be interesting. I did ballistic research at Columbia University some years ago (my son says it was for the Match lock)... we studied the ballistics of very small, high velocity particles in Helium and Methane - it was very interesting.
 
It seems to me that ES and timing are two separate topics that both relate to accuracy, in the case of ES, particularly long range.

As far as the desired timing of bullet exit, going back to Varmint Al's unique and excellent work, according to his research, and calculations, the best place for bullets to exit, on the barrels primary rise and fall (shown as where it points on a target) is just before it peaks and starts to descend. In this part of the curve, as the elastic limit is approached (my interpretation ) the curve flattens indicating a reduced change per unit of time. Given that shots will vary somewhat in velocity, this is the region where differences in velocity will be somewhat self compensating in terms of how much vertical spread is created solely from differences in speed. Slower rounds will leave when the barrel is pointing higher, and faster when it is pointing slightly lower. In looking at this for centerfire, a short range configured 6PPC was chosen, with appropriate barrel length, that was shorter than is normal for longer ranges, and the bullet weight was lighter and velocity higher than many long range situations, but the lessons were there to be learned. In that case, leaving the range of velocities within a group at something typical for that caliber and type of rifle, with the given barrel length, what was required was to slow the barrel's swing. Three methods would accomplish this. A weight on the muzzle, a longer barrel (24" in that case) or thinning the barrel in the middle of its length.

There has also been some discussion, particularly in the short range world, that alludes to observations that when all vertical is removed by tuning, that groups can spread out horizontally to an inordinate and undesirable degree. I think that this reinforces the idea of tuning for bullet exit when the barrel is near,but not at the peak of its rise.

This all goes to the primary balance of length and or muzzle weight and velocity, but what is overlooked is that there are evidently some higher harmonics involved as well. Evidence for this is in the observation tuners may be adjusted to multiple sweet spots, sometimes referred to as accuracy nodes, whereas the primary rise and fall of the barrel happens only once.

Then there is the discussion of what causes tune to change. To study this, I think that it would be a good idea to gather some data about the velocities where best accuracy occurred for a given rifle and set of components, in various locations and conditions. If it turned out that best accuracy was at a specific velocity, regardless of location or ambient conditions, then shooters would have a better idea of what they were trying to accomplish. It would also be interesting to learn if a single preload combined with tuner moves only could be made to serve under all conditions and at all locations. In any case, it would seem that making provision so that actual record shots might be fired over a chronograph might provide interesting data, and I can see no reason for not allowing this, as long as everyone was afforded the opportunity, perhaps sharing with shooters that who use the same bench.

Having stirred this pot a bit, my next task is to return to the kitchen for my second cup of coffee.
 
Boyd if I'm reading this right, I think that is what I'm trying to find! The load that will work in all conditions. Once I get there its shoot what you got!

Joe Salt
 
Joe Salt said:
Gene all or skills in Communication is lacking! Yes I believe you're right about the air, but most of my loads are done at home before I leave for the range, so if thing change that much in temp. and pressure, my groups do suffer. So I have to try and find the best load all the way around. There are times when I have noticed a change in elevation, I always save my zero from match to match. So is this on the same line you are talking about? Cause when my zero doesn't change I shoot well.

Joe Salt
Click to expand...



Joe, thanks for the kind words.

If you preload at home, you will still encounter different atmospheric conditions at the range which alter bullet exit timing (tune.) If you preload, sometimes you get lucky and the load will be just right for existing conditions and if temperature does not change appreciably throughout the day, you will shoot great, but,,,,, typically, temperature increases about 20 to 30 degrees from the first match of the morning to the last in the afternoon. If you have no way of compensating for these changes by varying the load or adjusting a tuner, your rifle will be in tune only about one fourth of the time.

In your post above, you said, "There are times in which I have noticed a change in elevation." I assume that by 'change in elevation' you are referring to changes in point of impact in the vertical plane. Is that correct? If so, this is often the result of slow mirage; mirage that displaces the target image. For many years, I was unaware of this 'slow mirage.' It was only after I started experimenting with a fixed reference scope that I came to realize just how much this so called 'slow mirage' could displace the target image. In my tunnel, it's not at all unusual to see target movement of a half inch in the vertical plane and about 1/8" in the horizontal, and it's slow, insidious, perfectly steady mirage not the shaky mirage you see outdoors. The only way I know to beat slow mirage is with a fixed reference scope.

After consulting with Dr. Jack Jackson, the editor of Vaughn's book, 'Rifle Accuracy Facts' I built my first fixed reference scope for use in the tunnel. It was a poor first effort because the mount was too flimsy and adjustments were difficult, but it worked! It opened my eyes! I have since built a much sturdier mount that bolts solidly to the benchtop with a half inch bolt; a semi-permanent installation but when necessary, it can be removed in about fifteen seconds using only a 3/4" wrench. I think you could anchor a battleship to it.

You said, "I always save my zero from match to match." I assume you mean you do not touch the scope adjustments from one day to the next; right? If so, I assure you the scope zero and point of impact will change from day to day, sometimes from one hour to the next. Oh,,, it will be close but not exactly the same no matter how expensive and perfect the scope and rifle are. Anything made of steel, glass, plastic, aluminum or whatever moves around from expansion and contraction with changes in temperature. This accounts for some of the change in zero, but atmospheric conditions and especially slow mirage also come into play.

Hope this helps. Thanks again for your post.

Gene Beggs
 
XBBR Shooter said:
Good evening Gene.

Some theories are hard or impossible to prove or even document...

... but your is easy. Take a can of computer cleaner (often called "Dust-off" or "canned air"), which is a halogen-carbon gas, and fill the bore with it before shooting and see if there is a noticeable difference, either in measured velocity (I doubt it) or in group. It would be interesting. I did ballistic research at Columbia University some years ago (my son says it was for the Match lock)... we studied the ballistics of very small, high velocity particles in Helium and Methane - it was very interesting.
Click to expand...



Thank you sir, I'll look into it.

Ballistic research at Columbia, eh? I'll bet that WAS interesting.
 
Joe Salt said:
Boyd if I'm reading this right, I think that is what I'm trying to find! The load that will work in all conditions. Once I get there its shoot what you got!

Joe Salt
Click to expand...



Joe, you will never find a load that will work in all conditions; at least not in benchrest. Oh sure,,, if you have a load that has the bullets exiting just before the top stop of the muzzle as it is on the upswing, the load window will be wider than the one at the bottom. But if you want to stay right on top of the tune, you must be able to compensate for increases in temperature by changing the load or adjusting a tuner. For some good information on this, study Rod Brown's article in the March issue of Precision Rifleman entitled, "Tuning With a Tuner."

Also, carefully review Boyd's post above. He knows what he's talking about.
 
Gene like I said you and boyd are the scientists, I'm the Rube Goldberg in this stuff, but sometimes it works. Gene about mirage I always thought of putting two scopes on a rifle is this what you were saying. But I thought of having one pointed a 50 yards and the other at 1000 so the mirage wouldn't make as much of a difference as what you were seeing at 1000! This on the same line.

Joe Salt
 
ekp said:
Is this the prevailing view of the community?

Can you elaorate?
Click to expand...

The prevailing view of what community??? Beginning shooters think it is OK... but they are always looking fr an easy way to get their loads to shoot. But they lack the ability to evaluate it to see if it really works, or if they just settled.

Any "system" that claims to give you perfect (or best) shooting solutions must be repeatable - id est, the same results over and over and over and over...

If you do "OCW" test targets, and repeat them with the same loads, so that you have a bunch of the same tests - mark then "A", "B", "C"... and then give the group of targets to someone that was not involved with the shooting... and ask them to evaluate the groups, they will not come up with a consistent result.

Further... if you repeat the tests, you do not get the same results.

And, statistically, if a rifle has a potential of 1" group size at 200 yds, and you fire a shot, then increase the load by 0.3 grains, the second shot can be above or below the first shot, depending on where in the statistics the shot fell. You could repeat only those two loads over and over, and NEVER get the same results... that is NOT what a true system does.

And, he says, "7. The primer brand you choose is entirely up to you. Use magnum primers only with magnum chamberings, as their added pressure may distort the OCW conclusions on standard chamberings. One exeption [sic] here would be with low density loads, as I believe that magnum primers improve ignition consistency in loads where the powder only fills 85 percent or less of the case."

This not true, and reflects a lack of basic knowledge and experience in loading. Magnum primers do not produce more pressure, they produce a longer heat profile because of non-explosive additives... sometimes this might give more pressure, but sometimes it produces less pressure.... but to state that magnum primers will distort any results, reveal a basic lack of knowledge of loading - if magnum primers make it impossible to develop reliable groups, then how do one explain that many shooters use magnum primers in standard chamberings with excellent results.

But this is what it really is all about...

He is in the long distance load developing business... "Email me and I will develop your load from my keyboard."

"Because of increasing demand (likely driven by the rising cost of reloading components), I'm now offering a one-on-one consulting service to personally assist you during your OCW load development process. Are you tired of getting those inexplicable "flyers" in your groups when you know that you didn't do anything wrong? Have you done ladder tests ad nauseum and you still haven't found a consistent load recipe? Is your load recipe so sensitive to minor changes that even a primer swap blows your accuracy? Would you like to learn how to make your cold, clean bore shot touch the rest of the group? Then keep reading...

I've counseled hundreds of shooters over the years by email and internet forums to help them find "the" load for their rifle and application. While these encounters have been quite successful (don't take my word for it, google search my name and "OCW" and see for yourself), written interaction does have its limitations. In literally dozens of cases I can remember finding out that a handloader had overlooked obvious hinderances to accuracy--and this we sometimes learned only after he'd spent a couple hundred bucks on components and range trips. Although many folks have become quite profficient at interpreting OCW targets, I still see that many are not. This means that simply shooting an OCW test is only part of the accuracy equation--you also need to properly interpret the data. Another concern is that we see folks adjusting the OCW process and "improving" it, sometimes by shooting at longer ranges than are prescribed, and/or by failing to shoot in round-robin fashion, or adding shots or taking shots away... All of these steps will work against you in the end.

Why hire a consultant?

First and foremost, you will save money. Very likely lots of money. If you'll be honest with yourself and carefully add up the cost of bullets and powder and primers and worn out brass and trips to the shooting range, you might be surprised just how much that magical load you finally arrived at has actually cost you. In a recent case, a man who had spent over 300 dollars chasing an accurate load for his .243 Winchester was led to a sub MOA load recipe in less than 20 shots.

I have compiled a database of handload information over the years that will allow me to steer you toward good combinations for your intended purpose--and away from bad ones. This alone will save you a considerable amount of money right from the start. Ballistics techs at the major bullet and powder makers don't always know what combinations work best. And like most handloaders, they tend to follow the age old "hunt and peck" method of load development, so any ideas you do get will have come from such processes.

Finally, there are many basics that some of us forget when it comes to shooting accurately. It simply takes too long to go over each and every one of these issues when we're interacting by email and forum posts alone. Often, we need phone consultation to really get to the bottom of what is going on.

If you choose to enlist my help for your load development endeavor, you will avail yourself of the following:

Absolute privacy. Your name and information will not be shared by me for any reason unless you specifically grant me permission to share your target photos and/or testimony.

Personal contact by phone on three to four occasions. In our initial conversation we'll discuss your rifle and scope combo, the purpose which you're using the rifle and load for, what components you may already have on hand which could work for you, and a sensible accuracy goal. In follow up phone conversations, we will discuss your targets (which you will send to me by email). We'll interpret the data, and consider seating depth adjustments that may improve your accuracy even more.

Email contact, continual. You can follow up at any time by email if you have further questions about your load and its performance. We'll plan to stay in touch long after we've gotten the load working for you.

A load that works. We will not stop until you're happy with the load you have. And during the process, you will learn much that will help you with other loads in the future.

------------------------------------------------------------------------------------------

The cost of my service is a very modest 45 dollars, which you can pay by credit card or paypal. That's less than a pound of powder and a box of bullets. And if you consider your time worth anything at all, factor that in as well. You have my promise that you will save time and money, and on top of that you'll arrive at a load recipe that will get all of the potential from your rifle.

Money back guarantee. In the unlikely event that we are unable to arrive at an acceptable load recipe for your rifle, I will gladly refund your 45 dollars, and you'll be no worse off than where you began. :)

If you have any questions, or if you are interested in my services, email me----> "danielnewberry@gmail.com"
 
Joe Salt said:
Gene about mirage I always thought of putting two scopes on a rifle is this what you were saying? Joe Salt
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No, what I was referring to is a separate, fixed-reference scope mounted to the bench. Its purpose is to detect 'slow mirage' the kind that permanently displaces the target image causing one to aim at the wrong spot.
 
Boyd Allen said:
... As far as the desired timing of bullet exit, going back to Varmint Al's unique and excellent work, according to his research, and calculations, the best place for bullets to exit, on the barrels primary rise and fall (shown as where it points on a target) is just before it peaks and starts to descend. In this part of the curve, as the elastic limit is approached (my interpretation ) the curve flattens indicating a reduced change per unit of time. ...
Click to expand...

It seems to be hard for people to get away from the "tune to the peak" concept. So hard that many, like Boyd (I don't mean to pick on you), just can't quite let it go and are now saying "just before the peak." In reality, the peak is unimportant. What we want is for the muzzle angle in the vertical plane to be increasing at just the right rate so that slow bullets are launched at a higher angle and hit the target at the same point as fast bullets. The necessary muzzle angular velocity can be calculated from external ballistics, though you will need a calculator that includes muzzle angle, which is not common. For a 30BR with muzzle velocities of 3012 and 3046 fps (these velocities were chosen for no other reason that they are from one of Varmint Al's simulations), I found 53 degrees per second to tune for 100 yards. (The optimal speed is different for other yardages.) I think this is in the ball park, since Geoffrey Kolbe measured 100 degrees per second to tune a rimfire at 50 meters. http://www.border-barrels.com/articles/rimfire_accuracy/tuning_a_barrel.htm

We also want the muzzle to have zero angular velocity in the horizontal plane. Horizontal muzzle angular velocity causes horizontal dispersion on the target, and there is no way to compensate for it. As we try different loads, tuner settings, etc., we may find a window where vertical angular velocity is just right, but we have significant horizontal velocity, so we get horizontal dispersion. This, I think, is what is interpreted as a wind sensitive tune. In reality, wind has nothing to do with it. It's just that barrel harmonics plus wind add up to more horizontal dispersion that we expected. Or we may find a window where horizontal velocity is near zero, and vertical velocity may or may not match the optimum. This is interpreted as a wind insensitive tune, when it is really just the nulling of barrel harmonics that reduced horizontal dispersion.

My $0.02,
Keith
 
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mks said:
It seems to be hard for people to get away from the "tune to the peak" concept. So hard that many, like Boyd (I don't mean to pick on you), just can't quite let it go and are now saying "just before the peak." In reality, the peak is unimportant. What we want is for the muzzle angle in the vertical plane to be increasing at just the right rate so that slow bullets are launched at a higher angle and hit the target at the same point as fast bullets. The necessary muzzle angular velocity can be calculated from external ballistics, though you will need a calculator that includes muzzle angle, which is not common. For a 30BR with muzzle velocities of 3012 and 3046 fps (these velocities were chosen for no other reason that they are from one of Varmint Al's simulations), I found 53 degrees per second to tune for 100 yards. (The optimal speed is different for other yardages.) I think this is in the ball park, since Geoffrey Kolbe measured 100 degrees per second to tune a rimfire at 50 meters. http://www.border-barrels.com/articles/rimfire_accuracy/tuning_a_barrel.htm

We also want the muzzle to have zero angular velocity in the horizontal plane. Horizontal muzzle angular velocity causes horizontal dispersion on the target, and there is no way to compensate for it. As we try different loads, tuner settings, etc., we may find a window where vertical angular velocity is just right, but we have significant horizontal velocity, so we get horizontal dispersion. This, I think, is what is interpreted as a wind sensitive tune. In reality, wind has nothing to do with it. It's just that barrel harmonics plus wind add up to more horizontal dispersion that we expected. Or we may find a window where horizontal velocity is near zero, and vertical velocity may or may not match the optimum. This is interpreted as a wind insensitive tune, when it is really just the nulling of barrel harmonics that reduced horizontal dispersion.

My $0.02,
Keith
Click to expand...

With acknowledgement to XBBR , his contribution and I do see his point, was not the premise of OCW to try to eliminate horizontal dispersion and then adjust the vertical with seating depth. I am not looking for a perfect system but everyone has a system of load development and I chose to try this one. Maybe the gentleman's real goal is to sell his services but that is the American way.
 
I don't know where you get your information. I have never written of tuning to the peak of the curve. The reference that I made was to Varmint Al's work that seems to indicate that the best area on his "where the muzzle is pointing on target" curve was just as I said, for the rifle loads and caliber that he was using as an illustration. Again, you have written that I a reluctant to let go of a position that I have never taken or written. If you are going to someone as an example, at least get your information correct. Evidently you have confused what someone else has written for what I have. As far as the rest of it goes, your idea of calculating the desired angle seems to be solid, and corresponds to thoughts that I have had but did not follow through on as well as you evidently have. I will count that as useful information for further study and consideration.
 
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