Canadian Bushman
Well-Known Member
I wonder why a ballistician would waste time testing a theory that simple geometry could disprove. Perhaps its not quite that simple?
Applied Ballistics 'Shoot Thru Target' Challenge
- Thread starter BryanLitz
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I wonder why a ballistician would waste time testing a theory that simple geometry could disprove. Perhaps its not quite that simple?
Bryan, thanks for being a sponsor and starting this interesting thread!
TAG
TAG
Thanks for the interest guys, I thought this would grab some attention!
Based on some input on another forum on this subject, I went on the shoot thru target today with the Desert Tech HTI in 375 CheyTac, a rifle which is well known to show non-linear dispersion, especially with the DTA loaded CE 352 grain MTAC bullet. Here's how it went.
All groups were fired from the bench.
Groups 1 thru 4 were fired with handloaded 352 grain CE MTAC bullets, loaded with 130 grains of Retumbo.
Group 1 was fired using the 100 yard point of aim, with the rear monopod support, and I got the same kind of group I'd seen in the past, vertically strung 2.07" at 100 yards, and it was 6.834" at 300 yards (1.98 MOA vs. 2.18 MOA).
After this group, I used a sandbag in the rear instead of the monopod which seemed to be a big improvement. From the ground where the support is 'softer', I think the monopod may produce better precision, I think the hard contact with the hard bench prevents it from shooting good groups.
Group 2 was fired using the 100 yard aim point, but with a sandbag support. This group measured 1.396" at 100 yards and 4.508" at 300 (1.33 MOA vs. 1.435 MOA).
Groups 3 and 4 were fired using the 300 yard aimpoint, and they were the best groups fired, but they still exhibited linear dispersion.
Group 3 grew from .846" at 100 to 2.409" at 300 (.81 vs .77 MOA). This group seems to exhibit a small amount of 'convergence' however it's only 5%. I can tell you from many tests in the past that up to 5% to 10% of convergence is common due to random wind and velocity effects. The same combinations don't always produce the same level of convergence. In other words, the ratio of MOA from 100 to 300 is expected to be 1.0 based on geometry, in reality the bullet holes show from .9 to 1.1 or 1.2 if the wind is bad. Group 3 had a 'convergence ratio' of 0.95.
Group 4 grew from .733" at 100 to 2.152" at 300 (.70 MOA vs .69 MOA). Again, although some convergence is seen, it's well within the 'noise' of the experiment, having a convergence ration of only 0.98.
Group 5 was the last 4 rounds of DTA loaded ammo I had on hand, which is basically the same as my handloads used for groups 1-4. Aim point was 100 yards, and the group went from 2.053 at 100 to 6.101" at 300 yards (1.96 MOA vs. 1.94 MOA) for a convergence ratio of 0.99.
Group 6 was CheyTac loaded 350 grain Balanced Flight bullets. Group was 3.102" at 100, and 10.147" at 300 (2.96 MOA vs 3.23 MOA) for a convergence ratio of 1.09.
In summary, this test failed to demonstrate group 'convergence' at a significant level.
However, I did find it very interesting that the two best groups were fired when the 300 yard aimpoint was used as opposed to the 100 yard aim point.
Disregarding groups 1 (monopod) and 6 (different ammo), Groups 2 and 5 were both fired using the 100 yard aimpoint. These groups (a 5-shot and a 4-shot group) averaged 1.68 MOA at all ranges. However, the two groups (groups 3 and 4, both 5-shot groups) were fired using the 300 yard aimpoints averaged 0.74 MOA at all ranges.
To me, that's the punchline of the day. Groups fired using the 100 yard aimpoint averaged 1.68 MOA at both ranges, while groups fired using the 300 yard aimpoint averaged 0.74 MOA at both ranges. NO significant group convergence was observed.
This result suggests a cause which is entirely optical/aiming related.
Some details regarding the aiming. I used a 5-25X NightForce ATACR scope, set to 25 power for all the shooting. Parallax was adjusted carefully prior to shooting each group. Aimpoints were 1" round circles at both 100 and 300 yards. I can tell you the 1" aimpoint looked 'big' at 100 yards, but was difficult to see behind the crosshairs at 300. Despite this difference in relative size of the aimpoints, it did not seem like the 300 yard aiming was anymore precise than the 100 yard aiming based on my perception.
Most of the shooting I've done in the past has all used the 100 yard aimpoints, because I've just been looking for the shot group convergence, and in that case it doesn't matter what aimpoint you use, just that you measure the group at two ranges. Today when I used two different aimpoints, it appeared to have a significant effect on the groups at both ranges.
Again, this strongly suggests an optical effect, but what, exactly? You can bet I'll be sharing this with all the 'optics' guru's I know and will report back if anything is turned up.
In the mean time, I plan to repeat this test, first with the same rifle and scope, then with various combinations to see if there's a common denominator in the scopes that produce this effect.
To circle back around to the monopod, I can see how (with this particular rifle), if you shoot 100 yards from the bench using the monopod you'll get 2" groups. Then if all your long range shooting is done from the softer ground (again using the monopod), the rifle may shoot much better from the ground than a hard bench when using the monopod. But this explanation would only apply to this (HTI) and other rifles with monopods.
The challenge is still on if anyone wants to come to MI. I'll even let you climb the tower to set the shoot thru target! (see attached pics)
-Bryan
Based on some input on another forum on this subject, I went on the shoot thru target today with the Desert Tech HTI in 375 CheyTac, a rifle which is well known to show non-linear dispersion, especially with the DTA loaded CE 352 grain MTAC bullet. Here's how it went.
All groups were fired from the bench.
Groups 1 thru 4 were fired with handloaded 352 grain CE MTAC bullets, loaded with 130 grains of Retumbo.
Group 1 was fired using the 100 yard point of aim, with the rear monopod support, and I got the same kind of group I'd seen in the past, vertically strung 2.07" at 100 yards, and it was 6.834" at 300 yards (1.98 MOA vs. 2.18 MOA).
After this group, I used a sandbag in the rear instead of the monopod which seemed to be a big improvement. From the ground where the support is 'softer', I think the monopod may produce better precision, I think the hard contact with the hard bench prevents it from shooting good groups.
Group 2 was fired using the 100 yard aim point, but with a sandbag support. This group measured 1.396" at 100 yards and 4.508" at 300 (1.33 MOA vs. 1.435 MOA).
Groups 3 and 4 were fired using the 300 yard aimpoint, and they were the best groups fired, but they still exhibited linear dispersion.
Group 3 grew from .846" at 100 to 2.409" at 300 (.81 vs .77 MOA). This group seems to exhibit a small amount of 'convergence' however it's only 5%. I can tell you from many tests in the past that up to 5% to 10% of convergence is common due to random wind and velocity effects. The same combinations don't always produce the same level of convergence. In other words, the ratio of MOA from 100 to 300 is expected to be 1.0 based on geometry, in reality the bullet holes show from .9 to 1.1 or 1.2 if the wind is bad. Group 3 had a 'convergence ratio' of 0.95.
Group 4 grew from .733" at 100 to 2.152" at 300 (.70 MOA vs .69 MOA). Again, although some convergence is seen, it's well within the 'noise' of the experiment, having a convergence ration of only 0.98.
Group 5 was the last 4 rounds of DTA loaded ammo I had on hand, which is basically the same as my handloads used for groups 1-4. Aim point was 100 yards, and the group went from 2.053 at 100 to 6.101" at 300 yards (1.96 MOA vs. 1.94 MOA) for a convergence ratio of 0.99.
Group 6 was CheyTac loaded 350 grain Balanced Flight bullets. Group was 3.102" at 100, and 10.147" at 300 (2.96 MOA vs 3.23 MOA) for a convergence ratio of 1.09.
In summary, this test failed to demonstrate group 'convergence' at a significant level.
However, I did find it very interesting that the two best groups were fired when the 300 yard aimpoint was used as opposed to the 100 yard aim point.
Disregarding groups 1 (monopod) and 6 (different ammo), Groups 2 and 5 were both fired using the 100 yard aimpoint. These groups (a 5-shot and a 4-shot group) averaged 1.68 MOA at all ranges. However, the two groups (groups 3 and 4, both 5-shot groups) were fired using the 300 yard aimpoints averaged 0.74 MOA at all ranges.
To me, that's the punchline of the day. Groups fired using the 100 yard aimpoint averaged 1.68 MOA at both ranges, while groups fired using the 300 yard aimpoint averaged 0.74 MOA at both ranges. NO significant group convergence was observed.
This result suggests a cause which is entirely optical/aiming related.
Some details regarding the aiming. I used a 5-25X NightForce ATACR scope, set to 25 power for all the shooting. Parallax was adjusted carefully prior to shooting each group. Aimpoints were 1" round circles at both 100 and 300 yards. I can tell you the 1" aimpoint looked 'big' at 100 yards, but was difficult to see behind the crosshairs at 300. Despite this difference in relative size of the aimpoints, it did not seem like the 300 yard aiming was anymore precise than the 100 yard aiming based on my perception.
Most of the shooting I've done in the past has all used the 100 yard aimpoints, because I've just been looking for the shot group convergence, and in that case it doesn't matter what aimpoint you use, just that you measure the group at two ranges. Today when I used two different aimpoints, it appeared to have a significant effect on the groups at both ranges.
Again, this strongly suggests an optical effect, but what, exactly? You can bet I'll be sharing this with all the 'optics' guru's I know and will report back if anything is turned up.
In the mean time, I plan to repeat this test, first with the same rifle and scope, then with various combinations to see if there's a common denominator in the scopes that produce this effect.
To circle back around to the monopod, I can see how (with this particular rifle), if you shoot 100 yards from the bench using the monopod you'll get 2" groups. Then if all your long range shooting is done from the softer ground (again using the monopod), the rifle may shoot much better from the ground than a hard bench when using the monopod. But this explanation would only apply to this (HTI) and other rifles with monopods.
The challenge is still on if anyone wants to come to MI. I'll even let you climb the tower to set the shoot thru target! (see attached pics)
-Bryan
Attachments
CB11WYO
Well-Known Member
Interesting. And good to know concerning monopod vs. sandbag vs. dirt vs. bench.
Good experiment!
barnesuser28
Well-Known Member
This type of investigation is the reason Applied Ballistics LLC is one of my favorite companies in the shooting industry. I applaud you for the time, money, and effort you have put into this and your books. Keep up the great work.
Riley
Riley
I'm going to say you don't have to worry about budgeting to cover travel expenses Bryan. I remain an ardent skeptic of the claims of non-linear dispersion, other than due to human and or optical causes. More care taken by the shooter at longer yardage, scope parallax or some other optical or atmospheric cause. Every now and then I've even read or heard that groups sizes measured at longer yardage measure a lesser dimension than groups measured at a closer yardage. As in 1" grouping at 100yds and 3/4" grouping at 200yds.
I've also experienced shooters that persistently claimed Coriolis effect didn't affect the flight of bullets from their rifles. Didn't cause any rightward drift in North America. There was a member of this forum that regularly posted again and again pictures of his 100-200yd groups being dead on left to right, and then pictures of his 1000 and 1200yd POIs also being dead on left to right. There are several possible explanations for this - rifle cant being just one. But the absence of coriolis drift on his bullets was his chosen explanation. Coriolis was nothing more than hocus pocus and abracadabra. Pixie dust.
For phenomena the human eye is unable to observe/detect, human brains are more than capable of explaining - often incorrectly.
I've also experienced shooters that persistently claimed Coriolis effect didn't affect the flight of bullets from their rifles. Didn't cause any rightward drift in North America. There was a member of this forum that regularly posted again and again pictures of his 100-200yd groups being dead on left to right, and then pictures of his 1000 and 1200yd POIs also being dead on left to right. There are several possible explanations for this - rifle cant being just one. But the absence of coriolis drift on his bullets was his chosen explanation. Coriolis was nothing more than hocus pocus and abracadabra. Pixie dust.
For phenomena the human eye is unable to observe/detect, human brains are more than capable of explaining - often incorrectly.
royinidaho
Well-Known Member
Hmmmm, this sounds interesting. I'm weird enough to give this a try.
One thing for sure, I'm going to ask my Dr. to check me for "epicyclic swerve" I think I've noticed some symptoms. :roll eyes:
My plan will be to have a 300 yard aim point and penetrate a 100 yard target and hit the 300 yard target.
Is that even optically possible? :roll eyes:
I'll be shooting some 352 grain brass tipped SMKs. Need some further testing on them.
Bryan, if it exhibits the phenom you're looking for, I stay in cold ol' Idaho and send the rig to MI...
One thing for sure, I'm going to ask my Dr. to check me for "epicyclic swerve" I think I've noticed some symptoms. :roll eyes:
My plan will be to have a 300 yard aim point and penetrate a 100 yard target and hit the 300 yard target.
Is that even optically possible? :roll eyes:
I'll be shooting some 352 grain brass tipped SMKs. Need some further testing on them.
Bryan, if it exhibits the phenom you're looking for, I stay in cold ol' Idaho and send the rig to MI...
Canadian Bushman
Well-Known Member
I think i gonna try to perform the same test but at 100 and 600.
I have a feeling its not gonna be easy, especially since im gonna try to use a 600 yd aim point.
I have a feeling its not gonna be easy, especially since im gonna try to use a 600 yd aim point.
Good test Bryan. I suggested something similar here once and was told the phenomenon of shrinking MOA groups at range does not need to be tested because it has been experimentally proven to happen. I don't deny it happens, I just think, as you do apparently, it has nothing to do with the bullet and external ballistics. Hopefully this discussion goes better than that one. People take scientific beliefs personally sometimes I think there will be many who will not believe your conclusions.
I think it matters because of load development and zeroing. The more we understand the better we can build rifles and scopes, and the better we can understand our own influence on the shots as shooters.
I think it matters because of load development and zeroing. The more we understand the better we can build rifles and scopes, and the better we can understand our own influence on the shots as shooters.
royinidaho
Well-Known Member
This it the first time that I've seen "open architecture" applied to something other than software and a BS session @ hunting camp.
Should be interesting to see it go through its growing cycle considering the spectrum of those potentially involved.
Should be interesting to see it go through its growing cycle considering the spectrum of those potentially involved.
nosualc
Well-Known Member
This is awesome.
I am very interested in your findings re: optical effect with regard to aim point. This could easily explain the phenomena.
I look forward to updates on your findings.
-nosualc
I am very interested in your findings re: optical effect with regard to aim point. This could easily explain the phenomena.
I look forward to updates on your findings.
-nosualc
bruce_ventura
Well-Known Member
Bryan, nice experiment. I applaud your attempt to resolve this question using the scientific method. That's not always easy to do in ballistics.
Parallax error could explain your results. If your rifle scope was focused at 300 yd and you shot all five groups with the same focus setting, your shot dispersion could have been effected by parallax error when aiming at the 100 yd target. That would have increased dispersion for both 100 and 300 yd groups when aiming at the 100 yd target.
Did you remove parallax error before aiming at the 100 yd target, and then again for the 300 yd target?
Parallax error could explain your results. If your rifle scope was focused at 300 yd and you shot all five groups with the same focus setting, your shot dispersion could have been effected by parallax error when aiming at the 100 yd target. That would have increased dispersion for both 100 and 300 yd groups when aiming at the 100 yd target.
Did you remove parallax error before aiming at the 100 yd target, and then again for the 300 yd target?
