Should have a lot more vertical

alinwa said:
LOL!!!

This pertickler drawing is kinda foofygucker :)

Once't you see the wavy line as "path of the bullet" it's hard to unsee
Click to expand...

The wavy line isn't the path of the bullet...it's the movement of the bore during firing. The length of the Full Cycle is more correctly the time of the Full Cycle.

Good shootin' :) -Al
 
Al Nyhus said:
The wavy line isn't the path of the bullet...it's the movement of the bore during firing. The length of the Full Cycle is more correctly the time of the Full Cycle.

Good shootin' :) -Al
Click to expand...

Oh I know dat...... Varmint Al at least has the sense to wrap a barrel around that part of the drawing http://www.varmintal.com/apres.htm


Edited to add, just for YOU Al, me bein' a bitchagain because I can

Actually that wavy line IS the path of the bullet LOL!!
 
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OliveOil said:
Al,

Is this that thread you are talking about ? http://benchrest.com/showthread.php?66948-A-Tale-Of-Three-Chrony-s

Thanks.
Click to expand...

It is not.... but it'll do :)

I probably posted about running congruent Chronos 3-4 times (??) and this was one of them. In this one I'm also testing lighting as lighting does affect accuracy..... (precision)

In other testing I went and bought these >> https://smile.amazon.com/Bulbrite-6...descent+lamp+frosted+bulb+dkes,aps,221&sr=8-6 << and set these three chronys up with consistent lights on the "skyscreens" and they registered more accurately.

With consistent artificial lighting on three in-line Shooting Chronys I got the agreement down to well under 5fps
 
BTW...... this test is tougher than it looks because velocity falls very rapidly near the muzzle and muzzle blast can muddle stuff up. LINEAR arrangements are hard to sort. It is very interesting to map velocity drop over 3ft-4ft-6ft (I kinda' expected them to be closer, as in "nearly the same" but with three chronos in ten feet you can easily see consistent velocity loss over very short distances :) which is why I've done further comparison testing using the magnetospeed and the Labradar. Magnetospeed is of no use to me, I bought one just for testing and gave it away when done....... but running a chronograph along with a Labradar (the Labradar basically hangs in my window frame all the time so it's constantly monitoring) I find wonderful agreement re precision. Even though the Labradar may show 20-50-80fps DIFFERENT. which I don't care about, I find all chronographs to be "accurate" as long as you can achieve consistent lighting. I mistrust a Shooting Chrony to be consistent thru clouds and the travel of the sun (angle). So when I use a chrony in the field I generally set up on a pivoting camera tripod, TIP IT OVER TO POINT AT THE GROUND and shine a bright light at the skyscreens.

All of this is very important to me because I require around 10fps ES on everything I shoot. I WILL just throw charges when playing around at 100yds because it makes it 'WAYYY easier to tune. But then I'll load to the kernel to find low ES in the center of a useful "node"

I find node tuning to be velocity-specific and have no fear of switching lots or even brands of powder
 
It was refreshing to see reference to Henry Childs. Henry has long since left this playground but WHATTA' guy. an Engineer of the first water.

Henry used to send me pix of his "reference chronograph" and data. Dude hung a log on chains Olde Schoole.... and had to add sapphire pivots because the chains offered "too much resistance".

Henry's opinions were more important than any many hundreds or thousands of others' because he VALIDATED them... Like Harold Vaughn he left this forum because he got sick of arguing with morons.

Henry's opinions, like Harold's perty much disagreed with everybody else in the world...... don't even get me STARTED on their (congruent) views of BC "variation" and "correction".... LOL
 
Before Henry gets offended and jumps in to correct me....(Or Boyd asks the elephant-in-the-room question) I said "sapphire pivots" just to sound all cool like dat. I'm prone to hyperole' for effect.

Obviously he actually used closed bearings the distribute and support for impact forces.
 
Also... one other wee thing ;)

sorry but I'm in the room now.

Just because it's sitting out there......"stability" has absolutely nothing to do with what you're observing. Stability can have no effect on the path of the bullet.
 
OliveOil said:
Kidding ??

or

you don't think a "bad" stability could have an influence on ACTUAL "in flight" ballistic coefficient, therefore changing the bullet path ??
Click to expand...

Not according to the ballistic Engineers whom I know and trust (there are only three IMO. Vaughn. Childs and Rinker) and not according to McCoy nor to any testing evidence. I once asked Harold Vaughn in person "should I test bullets for stability at 50yds and should I shy away from bullets that may take longer to go to sleep" and his reply was a derisive snort ...... "kid, I would have to teach you for a WEEK just to put that stupid question into perspective so short answer.... "NO!!! "stability" has NO MEASURABLE EFFECT on ballistic coefficient!!"


"And in any case, IF IT DID you cannot make "vary the BC of a group of bullets" enough to be measurable at 1000 yds." Now I'm not gonna' get into the 1000yd effects of "variable BC" because there are still beaucoup 1K shooters modifying their bullets and en masse they could take me.

So I'll just set that one out ;)

But here's the real kicker..... here's the logical reason it CANNOT be some mystical stability thing......BC/"stability"/flight path differences/flight time differences would make your group into LUCK!

It's NOT luck, it's a repeatable, reproducible and predictable phenomenon.

Your situation is quite simply a gravity drop over time problem and no matter how much you "change BC" you cannot in any way force the numbers to account for your experience. The bullets all timed the same and dropped the same....

The reason your bullets landed where they did is because the barrel BENT to put them there.
 
alinwa said:
Oh I know dat...... Varmint Al at least has the sense to wrap a barrel around that part of the drawing http://www.varmintal.com/apres.htm


Edited to add, just for YOU Al, me bein' a bitchagain because I can

Actually that wavy line IS the path of the bullet LOL!!
Click to expand...






Well....







kinda'







It's a stop-shot of the BORE at a point in time..... the flippin' whippin' trippin' road that the bullet rode ...... even though the bullet was never THERE on the line.....LOL



Schrodingers' Bullets?
 
test target

The bullet does follow the path set by the bbl's vibration pattern, no doubt. As for positive comp, I'm a believer and the science supports that but I think we have to think it through deeper. As in, how much pc is attainable by simply adding an adjustable weight to the end of the bbl with a gun that meets most orgs regs. There's a lot more to this than meets the eye. I'm not sure that 100% PC is even attainable with any gun design or weight at the bbl end. But I do think(know) that pc is a single component to tuning. The value of which, I can not quantify, even with a single given gun shape and bbl stiffness.

My tuner test is about quantifying the value of each adjustment of a tuner, just like should be done with powder charge. Otherwise, we're guessing when changing powder charge OR tuner setting.
Here's a pic of a tuner test fired by a customer, that does a very good job of showing the sine wave that is very typical to see. It's a little more clear in terms of the sine than of the group shapes but both are pretty apparent if you know what to look for. That said, I can't say that I can see any PC or that it matters as much as simply reading the groups and adjusting accordingly. I will say that, just like tuning with powder charge, if you're tuned to the "good side" of the sine pattern, pc can and does happen but there is no such thing as negative compensation...IME.

sine test.jpg
 
alinwa said:
Not according to the ballistic Engineers whom I know and trust (there are only three IMO. Vaughn. Childs and Rinker) and not according to McCoy nor to any testing evidence. I once asked Harold Vaughn in person "should I test bullets for stability at 50yds and should I shy away from bullets that may take longer to go to sleep" and his reply was a derisive snort ...... "kid, I would have to teach you for a WEEK just to put that stupid question into perspective so short answer.... "NO!!! "stability" has NO MEASURABLE EFFECT on ballistic coefficient!!"


"And in any case, IF IT DID you cannot make "vary the BC of a group of bullets" enough to be measurable at 1000 yds." Now I'm not gonna' get into the 1000yd effects of "variable BC" because there are still beaucoup 1K shooters modifying their bullets and en masse they could take me.

So I'll just set that one out ;)

But here's the real kicker..... here's the logical reason it CANNOT be some mystical stability thing......BC/"stability"/flight path differences/flight time differences would make your group into LUCK!

It's NOT luck, it's a repeatable, reproducible and predictable phenomenon.

Your situation is quite simply a gravity drop over time problem and no matter how much you "change BC" you cannot in any way force the numbers to account for your experience. The bullets all timed the same and dropped the same....

The reason your bullets landed where they did is because the barrel BENT to put them there.
Click to expand...



Thank you for your answer Al, but the link "BC stability ...". does not work (i suppose it's a link).


Here below a little experience I was able to reproduce 3 times.

I am shooting 660 yd.

Got ammo loaded full throttle, with either N140 or N150, all other things beeing equal.

Shot 10 of a kind then 10 of the other kind to get an average ""muzzle" velocity for each kind.

Move the PACT to 660 yd (and yes, the skyscreens feet are all plywood or cotton fabric and expoxy)

Shot again 10 of a kind and 10 of the other kind, getting an average 660 yd velocity for each.

Going to JBM with ""muzzle" and 660 yd velocities gave me a BC for each kind.


The N140 BC was always (3 times) 10-12% superior to the N150 BC.

Please note I am not talking group size or group location on target, just calculated BC from velocity decay measurement. It's not random, it always pointed to the same 10-12% result in favor of the N140 loading. So that's not about pact accuracy, any std dev in any place.



How would you explain that ?
 
1st problem;

So sorry......That is not a link I just underlined it for emphasis, my bad! I am just pointing out that if LUCK put the bullets into the group then it's a fluke, a one-off, not repeatable. But in the real world folks shoot groups with pretty tall ES into the same hole, LOTS of folks.I do suspect that due to the shape of the groups in Mikes image, the man shooting them was weighing his charges precisely.


2nd problem;

IF what you're saying is that you launched identical bullets under identical conditions and identical velocities and the ones launched with one powder showed 10%-12% different BC's..... I have no idea.

I do see why you attribute "stability" to the conundrum. I'll have to set and think some on this thing.

Thank you for a clear, concise problem.
 
Could be the 'weebol' between the wobbles . . .

OliveOil said:
Thank you for your answer Al, but the link "BC stability ...". does not work (i suppose it's a link).


Here below a little experience I was able to reproduce 3 times.

I am shooting 660 yd.

Got ammo loaded full throttle, with either N140 or N150, all other things beeing equal.

Shot 10 of a kind then 10 of the other kind to get an average ""muzzle" velocity for each kind.

Move the PACT to 660 yd (and yes, the skyscreens feet are all plywood or cotton fabric and expoxy)

Shot again 10 of a kind and 10 of the other kind, getting an average 660 yd velocity for each.

Going to JBM with ""muzzle" and 660 yd velocities gave me a BC for each kind.


The N140 BC was always (3 times) 10-12% superior to the N150 BC.

Please note I am not talking group size or group location on target, just calculated BC from velocity decay measurement. It's not random, it always pointed to the same 10-12% result in favor of the N140 loading. So that's not about pact accuracy, any std dev in any place.



How would you explain that ?
Click to expand...

OliveOil, interesting test: for each string, what was the variation in BC? Over the three outings, did the [BC] variation, within each string (powder), repeat? Curious in paradise, RG
 
Well, I've set and thought;

I can find no mechanism, no causal factor to link your experiences.

#1, chrono error..... I can't rule this out of course but I don't see HOW a radar unit can get bad readings and it doesn't register blast as velocity, only as a trigger. A radar speed reading is "digital" VS "Analog" in that it READS, or it doesn't and while it's "reading range" need be adjusted for velocity it's not affected by lighting angles reading bullet shadow or glint.


#2, stability variation..... Can't find any link. Even if the faster bullets were somehow unstable, slowed down and dropped into the group.
 
OliveOil said:
Thank you for your answer Al, but the link "BC stability ...". does not work (i suppose it's a link).


Here below a little experience I was able to reproduce 3 times.

I am shooting 660 yd.

Got ammo loaded full throttle, with either N140 or N150, all other things beeing equal.

Shot 10 of a kind then 10 of the other kind to get an average ""muzzle" velocity for each kind.

Move the PACT to 660 yd (and yes, the skyscreens feet are all plywood or cotton fabric and expoxy)

Shot again 10 of a kind and 10 of the other kind, getting an average 660 yd velocity for each.

Going to JBM with ""muzzle" and 660 yd velocities gave me a BC for each kind.






The N140 BC was always (3 times) 10-12% superior to the N150 BC.

Please note I am not talking group size or group location on target, just calculated BC from velocity decay measurement. It's not random, it always pointed to the same 10-12% result in favor of the N140 loading. So that's not about pact accuracy, any std dev in any place.



How would you explain that ?
Click to expand...

You don't say what the muzzle velocities are.
 
P. Octo said:
View attachment 25770

Sorry, I can't turn the picture upright, but my question is why not a lot more vertical?
I was shooting a LV Krieger 6PPC barrel, Berger Column, moly coated, on top of 29.8gr of V 133 at 100 meters. Wind was about 2.5 m/s from 1 to 3 o'clock with occasional gusts at 5 m/s. As I was testing the Column in this barrel I didn't hold for vertical and on that particular target I held a tad less than the 1/8" dot laterally. Now, The Labradar gave:

3412 ft/s
3343
3330
3340
3451

With such a huge difference in velocity I'd have expected a ladder! Also, strange enough to me, the velocity at 25m didn't reflect the differences at V1; the 3451 and the 3330 difference of 121 ft/s dropped to about 33 ft/s. No explanation. The cases had been through a few matches but annealed on the AMP machine and checked on the ICC, trimmed, etc., the work... Powder had been weighed and put in tubes; temperature was 13°C (55°F), humidity 39%.
I was tempted to suspect the Labradar readings of the V1 shots (reading the blast?) but that seems farfetched.
Click to expand...


Sorry, I do not have the answer to your question; as I am not exactly sure how one reads a group that was shot with a two hour variance, gusts doubling in velocity and not knowing when the trigger was pulled.

No question on the vc but think that has more value at long range.

Question: Were the lower sighters shot with the same conditions. Lots of vertical there when compared to center group.

Off subject but, where was your holding point, I like my POI down wind of my POA.?

Bonne chance!
 
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Howdy Ken

K Hope said:
Sorry, I do not have the answer to your question; as I am not exactly sure how one reads a group that was shot with a two hour variance, gusts doubling in velocity and not knowing when the trigger was pulled.

No question on the vc but think that has more value at long range.

Question: Were the lower sighters shot with the same conditions. Lots of vertical there when compared to center group.

Off subject but, where was your holding point, I like my POI down wind of my POA.?

Bonne chance!
Click to expand...

How are you winterin?

Pete
 
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