Canadian Bushman
Well-Known Member
Im curious to see how this works out since i no longer belive my "bullet wobble" is to blame.
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Applied Ballistics 'Shoot Thru Target' Challenge
- Thread starter BryanLitz
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Im curious to see how this works out since i no longer belive my "bullet wobble" is to blame.
Spent all day at the lab on the shoot thru target today, and all evening analyzing results.
Here's the synopsis.
I shot 3 different target set-ups, each with a different rifle/ammo combination.
First group was the .375 CT using 1 MOA aimpoints at both 100 and 300 yards. I shot 3 groups at each range (two of the groups were 5-shots, and the third group was 3-shots). A summary of the results:
None of the groups showed signifficant non-linear dispersion; meaning; the groups were proportional in size at 300 compared to 100.
The three groups fired using the 1" 100 yard aimpoint ranged from .59 MOA to 1.27 MOA, with an average of 1.53 MOA.
The three groups fired using the 3" 300 yard aimpoint ranged from .39 MOA to 2.8 MOA, with an average of 1.73 MOA.
Statistically speaking, there is no difference between aiming at 100 vs. 300 when the aimpoints are both 1 MOA.
Moving on to the second test, we took the scope off the 375 CT and put it on a .308 Win 'Lab gun' which is a workhorse consisting of a Savage action, Bartlein barrel, HS Precision stock, and Madison Bi-Pod. Ammo was 200 grain Berger Hybrids. On this target we fired 6 groups using the 100 yard aimpoint, and 5 groups using the 300 yard aimpoint. Again, none of the 11 total groups exhibited 'convergence'.
The 6 groups fired using the 1" 100 yard aimpoint ranged from 0.34 MOA to 1.04 MOA with an average of 0.66 MOA.
The 5 groups fired using the 3" 300 yard aimpoint ranged from 0.51 MOA to 1.05 MOA with an average of 0.77 MOA.
Again, there is no statistically significant difference in average group size between aiming at the 1 MOA 100 yard aimpoint and the 1 MOA 300 yard aimpoint.
The last test was fired with the same rifle, but with ammo loaded with Berger 175 OTM bullets. This time, 1" aimpoints were used on both the 100 and 300 yard targets. This test was designed around the 'aim small, miss small' idea. 4 groups were fired at each aim point. Again, the average of the 8 groups showed no group convergence.
The four groups fired using the 1" 100 yard aimpoint ranged from 0.39 MOA to 0.57 MOA, with an average of 0.48 MOA.
The four groups fired using the 1" 300 yard aimpoint ranged from 0.34 MOA to 0.47 MOA with an average of 0.39 MOA.
I'll have to brush up on my statistics in the morning in order to figure out the actual correlation, but based on the above, I think we can *statistically* say that there is more than a 50% chance that there is a correlation between aiming at 300 vs. 100 yards when the aimpoint is 1" in both cases.
When the aimpoint was 1 MOA in both cases (1" at 100 and 3" at 300), the correlation was much weaker and actually favored the 100 yard aimpoint slightly.
Going back to the test on page 3, that test also used 1" aimpoints at both ranges, and there appeared to be a strong correlation to what range was aimed at.
This is also in alignment with Canadians test.
One thing is becoming more clear; and that is that bullets don't actually fly converging flight paths. None of the groups fired on the shoot thru target exhibit this behavior consistently or significantly.
The strongest correlation that has been established so far is aiming at 100 vs. 300, but only when the aimpoint is angularly smaller at distance (1" at both ranges).
Conceptually, this makes sense if you think about it in terms of extremes. Imagine shooting groups at a 100 yard aimpoint that's 5" big, then shooting groups at an aimpoint that's 0.5" big. It seems clear that you would be able to resolve your aim better and shoot a smaller group using the 0.5" aimpoint vs. the 5", so why wouldn't the same be true when shooting a 1" aimpoint at 100 vs a 1" aimpoint at 300 yards (1 MOA vs. 1/3 MOA)? I'll have a good laugh at myself if this whole thing can be demonstrated using 1/3" vs. 1" aimpoints at 100 yards!
Of course this question is long form settled, but I'm excited to finally have a theory which appears to be correlating. Not the first time I thought I was on to something! But this theory is based on a good amount of shooting. It's easy to see all kinds of things with a small number of 3 or 5 shot groups. But in order to discover trends which are real (meaning statistically signifficant and repeatable) it sometimes takes many shots and many groups to overcome the statistical uncertainty inherent in group sizes by nature. I think the data gathered during todays test is a step in that direction, but I'm sure I'll be climbing the tower to the shoot-thru target many more times before I'll be satisfied calling this one settled.
Here's the synopsis.
I shot 3 different target set-ups, each with a different rifle/ammo combination.
First group was the .375 CT using 1 MOA aimpoints at both 100 and 300 yards. I shot 3 groups at each range (two of the groups were 5-shots, and the third group was 3-shots). A summary of the results:
None of the groups showed signifficant non-linear dispersion; meaning; the groups were proportional in size at 300 compared to 100.
The three groups fired using the 1" 100 yard aimpoint ranged from .59 MOA to 1.27 MOA, with an average of 1.53 MOA.
The three groups fired using the 3" 300 yard aimpoint ranged from .39 MOA to 2.8 MOA, with an average of 1.73 MOA.
Statistically speaking, there is no difference between aiming at 100 vs. 300 when the aimpoints are both 1 MOA.
Moving on to the second test, we took the scope off the 375 CT and put it on a .308 Win 'Lab gun' which is a workhorse consisting of a Savage action, Bartlein barrel, HS Precision stock, and Madison Bi-Pod. Ammo was 200 grain Berger Hybrids. On this target we fired 6 groups using the 100 yard aimpoint, and 5 groups using the 300 yard aimpoint. Again, none of the 11 total groups exhibited 'convergence'.
The 6 groups fired using the 1" 100 yard aimpoint ranged from 0.34 MOA to 1.04 MOA with an average of 0.66 MOA.
The 5 groups fired using the 3" 300 yard aimpoint ranged from 0.51 MOA to 1.05 MOA with an average of 0.77 MOA.
Again, there is no statistically significant difference in average group size between aiming at the 1 MOA 100 yard aimpoint and the 1 MOA 300 yard aimpoint.
The last test was fired with the same rifle, but with ammo loaded with Berger 175 OTM bullets. This time, 1" aimpoints were used on both the 100 and 300 yard targets. This test was designed around the 'aim small, miss small' idea. 4 groups were fired at each aim point. Again, the average of the 8 groups showed no group convergence.
The four groups fired using the 1" 100 yard aimpoint ranged from 0.39 MOA to 0.57 MOA, with an average of 0.48 MOA.
The four groups fired using the 1" 300 yard aimpoint ranged from 0.34 MOA to 0.47 MOA with an average of 0.39 MOA.
I'll have to brush up on my statistics in the morning in order to figure out the actual correlation, but based on the above, I think we can *statistically* say that there is more than a 50% chance that there is a correlation between aiming at 300 vs. 100 yards when the aimpoint is 1" in both cases.
When the aimpoint was 1 MOA in both cases (1" at 100 and 3" at 300), the correlation was much weaker and actually favored the 100 yard aimpoint slightly.
Going back to the test on page 3, that test also used 1" aimpoints at both ranges, and there appeared to be a strong correlation to what range was aimed at.
This is also in alignment with Canadians test.
One thing is becoming more clear; and that is that bullets don't actually fly converging flight paths. None of the groups fired on the shoot thru target exhibit this behavior consistently or significantly.
The strongest correlation that has been established so far is aiming at 100 vs. 300, but only when the aimpoint is angularly smaller at distance (1" at both ranges).
Conceptually, this makes sense if you think about it in terms of extremes. Imagine shooting groups at a 100 yard aimpoint that's 5" big, then shooting groups at an aimpoint that's 0.5" big. It seems clear that you would be able to resolve your aim better and shoot a smaller group using the 0.5" aimpoint vs. the 5", so why wouldn't the same be true when shooting a 1" aimpoint at 100 vs a 1" aimpoint at 300 yards (1 MOA vs. 1/3 MOA)? I'll have a good laugh at myself if this whole thing can be demonstrated using 1/3" vs. 1" aimpoints at 100 yards!
Of course this question is long form settled, but I'm excited to finally have a theory which appears to be correlating. Not the first time I thought I was on to something! But this theory is based on a good amount of shooting. It's easy to see all kinds of things with a small number of 3 or 5 shot groups. But in order to discover trends which are real (meaning statistically signifficant and repeatable) it sometimes takes many shots and many groups to overcome the statistical uncertainty inherent in group sizes by nature. I think the data gathered during todays test is a step in that direction, but I'm sure I'll be climbing the tower to the shoot-thru target many more times before I'll be satisfied calling this one settled.
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royinidaho
Well-Known Member
Bryan,
Why does everything worth doing take so much darn time??
It seems that some significance may be attributed to the resolution of the human eye.
Each of us has different abilities in that area.
I recall that one of baseball's great hitters was able to see the spin of the stitching on the 90 MPH baseball and react accordingly.
Look at a dial caliper and discern the value between the marks. Just think'n out loud.
Why does everything worth doing take so much darn time??
It seems that some significance may be attributed to the resolution of the human eye.
Each of us has different abilities in that area.
I recall that one of baseball's great hitters was able to see the spin of the stitching on the 90 MPH baseball and react accordingly.
Look at a dial caliper and discern the value between the marks. Just think'n out loud.
cowboy
Well-Known Member
You now have my vote on being on the right course.
I also agree with the above that there is a difference in individual eyesight. I personally shoot better MOA at distance using the smallest diamond shaped point of aim I can comfortable see that is sky blue in color versus a black or say red outlined diamond. Maybe it's in my head but my caliper says I shoot better groups.
If you want to buy me a plane ticket I'll bring you quite a few rifles that will repeat your results of today.
Keep up the good work. You have the credibility to finally put this old myth of wobbling bullets to bed.
dmoran
Member
Brian -
Don't have time for much of a reply, but in short, it is to my experience you need wind to see Non-linear dispersion to much of any degree. Not sure what your lab capabilities are but having some extra drag on the bullets aids to the scenario is my experience.
Sent you a PM......
Good conversation !.!.!
Donovan Moran
Don't have time for much of a reply, but in short, it is to my experience you need wind to see Non-linear dispersion to much of any degree. Not sure what your lab capabilities are but having some extra drag on the bullets aids to the scenario is my experience.
Sent you a PM......
Good conversation !.!.!
Donovan Moran
The only two things that could cause this are the shooter themselves by not trying thier best at shorter distances, which is probably pretty common but I doubt its the reason, or external ballistics on top of any inconsistecy round to round and how it leaves the barrel. A precision muzzle crown could still be off a few hundreds of thousandths on one side, not much but it will effect the projectile.
Any bullet leaving a barrel will try to remain on its original trajectory, but gravity and wind resistance cause it to slow down and drop off that launch angle. Imagine your bullet is an aircraft and someone has given it a lot of rudder when its leaves the barrel, the bullet even though it may have come out a little crooked for whatever reason will try start to self correct to the most aerodynamic position possible simply because there is more resistance on one side, Now lets take that aircraft and send it into a spin like a bullet and still give it yaw, as soon as the control surfaces are retured to zero the airplane will try to resume a striahgt flight path, it may still be spinning but it will return to a neutral yaw.
Thats exactly what a bullet is doing only it doesnt have pesky wings to mess with its flight, Its moving on sheer inertia alone, so your bullet comes out of your barrel with a little yaw, its *** in hanging out to one side but its spinning so you not only have a force greater on the side hanging out in the wind since its rotating there is also a lateral force of wind resistance and centrifugal force trying to keep that tail hanging out, but since the lateral force is eventually overcome by the linear force of wind trying to correct the bullet as it loses speed therefore inertia, the bullet must correct into a more aerodynamic flight path, it will eventually normalize.
Take the .338 in the example where it keyholed at 300 but was true at 100, and remained accurate even though it wasnt flying true, obviously bullet type and sectional density play a part, but what I think is happening is the bullet is coming out with so much force that any little bit of yaw cant overcome its inertia and tendency to stay true to that initial launch angle and trajectory, but once a little speed and energy bleeds off the centrfugal force and the slight yaw begin to overcome the sheer speed and energy of the projectile leaving the barrel and become unstable and yaw significantly as evidenced by keyholing,, then again the bullet will return to a more aerodynamically stable flight when the centrifugal force keeping the bullet yawing will be overcome by wind resistance and self correct. leading to a more accurate representation of the initial flight path down range.
That means that since the bullet is going through all of this self correcting it may not be as accurate at closer ranges as the bullet weight and velocity increase because even though its being moved around by its own spin and yaw, it is still doing everything it can to remain on its original path of flight, and will eventually return to it as the flight stabilizes, compared to a 22lr that will tack drive at 50-100yds but cant keep anything near that accuracy as you go out to 200 simply because the loss of velocity and a very low BC cant overcome any wind it meets.
I suspect that the higher the BC, bullet weight and velocity are the more of a non linear dispersion you will see. And since I only have .224 caliber rifles that can achieve any sort of real sub minute accuracy I doubt ill see any sort of increased accuracy phenomenon. That is if my theory is correct, I could be so far off its not even funny.
The only way to prove this as I see it would be to capture the bullets flight in its entirety on high speed film or build one long *** range that can be turned into a vacuum chamber and somehow fire a round into it without losing that vacuum and watch as the bullet just yaws wildly out of control because there is only gravity effecting its path, and no self correcting forces from wind resistance.
Id like to hear what a true ballistician thinks of all this, I mean I use Applied Ballistics for crying out loud Im a kindergardener when it comes to this stuff compared to Bryan Litz.
Any bullet leaving a barrel will try to remain on its original trajectory, but gravity and wind resistance cause it to slow down and drop off that launch angle. Imagine your bullet is an aircraft and someone has given it a lot of rudder when its leaves the barrel, the bullet even though it may have come out a little crooked for whatever reason will try start to self correct to the most aerodynamic position possible simply because there is more resistance on one side, Now lets take that aircraft and send it into a spin like a bullet and still give it yaw, as soon as the control surfaces are retured to zero the airplane will try to resume a striahgt flight path, it may still be spinning but it will return to a neutral yaw.
Thats exactly what a bullet is doing only it doesnt have pesky wings to mess with its flight, Its moving on sheer inertia alone, so your bullet comes out of your barrel with a little yaw, its *** in hanging out to one side but its spinning so you not only have a force greater on the side hanging out in the wind since its rotating there is also a lateral force of wind resistance and centrifugal force trying to keep that tail hanging out, but since the lateral force is eventually overcome by the linear force of wind trying to correct the bullet as it loses speed therefore inertia, the bullet must correct into a more aerodynamic flight path, it will eventually normalize.
Take the .338 in the example where it keyholed at 300 but was true at 100, and remained accurate even though it wasnt flying true, obviously bullet type and sectional density play a part, but what I think is happening is the bullet is coming out with so much force that any little bit of yaw cant overcome its inertia and tendency to stay true to that initial launch angle and trajectory, but once a little speed and energy bleeds off the centrfugal force and the slight yaw begin to overcome the sheer speed and energy of the projectile leaving the barrel and become unstable and yaw significantly as evidenced by keyholing,, then again the bullet will return to a more aerodynamically stable flight when the centrifugal force keeping the bullet yawing will be overcome by wind resistance and self correct. leading to a more accurate representation of the initial flight path down range.
That means that since the bullet is going through all of this self correcting it may not be as accurate at closer ranges as the bullet weight and velocity increase because even though its being moved around by its own spin and yaw, it is still doing everything it can to remain on its original path of flight, and will eventually return to it as the flight stabilizes, compared to a 22lr that will tack drive at 50-100yds but cant keep anything near that accuracy as you go out to 200 simply because the loss of velocity and a very low BC cant overcome any wind it meets.
I suspect that the higher the BC, bullet weight and velocity are the more of a non linear dispersion you will see. And since I only have .224 caliber rifles that can achieve any sort of real sub minute accuracy I doubt ill see any sort of increased accuracy phenomenon. That is if my theory is correct, I could be so far off its not even funny.
The only way to prove this as I see it would be to capture the bullets flight in its entirety on high speed film or build one long *** range that can be turned into a vacuum chamber and somehow fire a round into it without losing that vacuum and watch as the bullet just yaws wildly out of control because there is only gravity effecting its path, and no self correcting forces from wind resistance.
Id like to hear what a true ballistician thinks of all this, I mean I use Applied Ballistics for crying out loud Im a kindergardener when it comes to this stuff compared to Bryan Litz.
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Bryan,
Thanks for such a great thread and effort in bringing your test results to us.
It's a long way from Aus. to Michigan so good thing all my rifles don't exhibit this phenomenon… LOL.
I do have a question for you, is this phenomenon talked about in Full Bore shooting? Do you hear of this happening with the use of peep sights or is it limited only to people who shoot with scopes?
If Full Bore shooters have observed this phenomenon then it would seem possible to go through the results of high class Full Bore matches at different distances and see if the same shooter/rifle combination regularly performed better at longer distance than at some shorter distance.
Thanks for such a great thread and effort in bringing your test results to us.
It's a long way from Aus. to Michigan so good thing all my rifles don't exhibit this phenomenon… LOL.
I do have a question for you, is this phenomenon talked about in Full Bore shooting? Do you hear of this happening with the use of peep sights or is it limited only to people who shoot with scopes?
If Full Bore shooters have observed this phenomenon then it would seem possible to go through the results of high class Full Bore matches at different distances and see if the same shooter/rifle combination regularly performed better at longer distance than at some shorter distance.
Topshot,
Good question. There are some insights to be gained from FULLBORE.
First, there's the issue of bullet selection for short vs. long range. Some have advocated using FB bullets in the 135-150 grain range for 300 and even up to 500 or 600 yards depending on conditions. The idea being the FB bullets have better inherent precision, and at short range, won't suffer as much from inferior ballistics (wind deflection). The 155 BT's, and as disciplines allow, up to 210 grain bullets can shoot higher scores at long range due to ballistic advantage, but their not as precise at 300 where ballistics isn't as much of an issue.
This is just a matter of balancing ballistic performance and precision and choosing the optimal bullet for the range.
Another consideration is specific to sight picture. How big does the 'black' appear in the aperture sights can affect ones ability to aim precisely. There's a lot going on here, and I know for sure it depends on individual preference especially how much 'white' a shooter likes to see between the black bullseye and the inside of the front sight aperture. I remember when I started shooting iron sights, I used a narrow line of white because I believed it helped resolve better aiming since you could more easily see any small misalignment. However, many top shooters kept telling me they used a large band of white, so I tried it. It was a surprise when my scores went up using a wider band of white. I can't fully explain this, but there's no doubt I shoot better with more white than my logic would have suggested.
Traditionally, many US FULLBORE shooters struggle with the international 300 yard target. One of the prevailing theories is that target has a larger black, and our sight apertures don't open up large enough to allow us to get the sight picture we can get with every other target. As a shooter, the sight picture doesn't 'look' bad, but there's few other theories as to why we drop so many points on that 300 yard target.
Of course some have advanced the theory of epicyclic swerve to explain the trouble at 300 yards, saying the bullets aren't settled down enough at that range. But then you have those who use the same theory to explain how bullets shoot big at 100 and aren't 'settled' until 200 where they shoot small.
Take care,
-Bryan
Good question. There are some insights to be gained from FULLBORE.
First, there's the issue of bullet selection for short vs. long range. Some have advocated using FB bullets in the 135-150 grain range for 300 and even up to 500 or 600 yards depending on conditions. The idea being the FB bullets have better inherent precision, and at short range, won't suffer as much from inferior ballistics (wind deflection). The 155 BT's, and as disciplines allow, up to 210 grain bullets can shoot higher scores at long range due to ballistic advantage, but their not as precise at 300 where ballistics isn't as much of an issue.
This is just a matter of balancing ballistic performance and precision and choosing the optimal bullet for the range.
Another consideration is specific to sight picture. How big does the 'black' appear in the aperture sights can affect ones ability to aim precisely. There's a lot going on here, and I know for sure it depends on individual preference especially how much 'white' a shooter likes to see between the black bullseye and the inside of the front sight aperture. I remember when I started shooting iron sights, I used a narrow line of white because I believed it helped resolve better aiming since you could more easily see any small misalignment. However, many top shooters kept telling me they used a large band of white, so I tried it. It was a surprise when my scores went up using a wider band of white. I can't fully explain this, but there's no doubt I shoot better with more white than my logic would have suggested.
Traditionally, many US FULLBORE shooters struggle with the international 300 yard target. One of the prevailing theories is that target has a larger black, and our sight apertures don't open up large enough to allow us to get the sight picture we can get with every other target. As a shooter, the sight picture doesn't 'look' bad, but there's few other theories as to why we drop so many points on that 300 yard target.
Of course some have advanced the theory of epicyclic swerve to explain the trouble at 300 yards, saying the bullets aren't settled down enough at that range. But then you have those who use the same theory to explain how bullets shoot big at 100 and aren't 'settled' until 200 where they shoot small.
Take care,
-Bryan
Mr Litz,
Thank you for taking this on! I've participated in many discussion on this topic over the 20 or so years I've been on the internet and I have a few anecdotes to share from these discussion over the years.
Early on, the subject intrigued me so much that I called Bill Davis at Tioga Engineering to pose the question to him. He was very patient and indulgent in answering my query. He told me that he had never observed the phenomenon, but did not rule it out. I shared with him the viewpoint of the proponents (corkscrew path, bullet goes to sleep downrange) to which he replied that bullet swerve did exist, but it was very small, on the order of a fraction of a caliber. He immediately started reasoning through a way to empirically test the existence using an onion paper target at short range so as not to upset the path of the bullet as it continued downrange. (through the years, I proposed acoustic targets as even less disruptive as they became available). That he did not discount it entirely and was thinking of ways to test for the phenomenon impressed me. I was sad to only recently find out that he is no longer with us.
One of the anecdotes that is commonly brought up by the proponents of bullets going to sleep and causing smaller groups down range that at close range is the Gale McMillan experience testing 50 cal sniper rifles. Rather than recount his writings here, I'll see if I can find a link through the magic of the internet. In short, Mac observed in shooting thousands of rounds of 50 BMG that they grouped smaller at 1000 yds than at the shorter distances. (hence there might be value in tapping the 50 cal crowd to take up the challenge since sadly Mac is also no longer with us).
I personally find it hard to reason through how the many forces acting to disrupt a bullet's path can be magically reversed. I believe Harold Vaughn offered similar explanations of why people were observing this phenomenon (scope parallax and bad statistics) in his book.
There is one very specific case of the phenomenon that remains credible for me though. It was touched on by Zfastmalibu; Positive Compensation, which helped to explain dispersion in the vertical plane only. The history of positive compensation goes back to the British fullbore experience. In the early days, the ball ammo used for long range was terrible for ES, and the Enfields were quite "whippy". Some smart brit figured out you could harness the both to allow for the slower rounds to be released from the barrel at a higher point in the whip and the faster rounds at a lower point. The result was rounds that would converge for vertical at the desired range (typically 1000 yards). GE Fulton was reknown for tuning or "regulating" Enfields to produce this effect. There's a short article of this in the old NRA Highpower Series that I'm going to guess you already have, but that I will dig up and try to scan for the crowd here. It mentioned that compensation was also seen in M14's though in a lesser degree.
Lastly, I have a good friend and fellow service rifle competetor that swears his AR with 80's and 90's group tighter at 300 yards than at 100yds. We get along great otherwise, and even worked well together in sorting out the 90gr JLK's out of an AR Service Rifle (I ran the pressures on his loads to ensure the speed freak didn't blow himself up). I'm going to see if I can get him to take on your challenge.
Thanks for continuing to do the good work.
Thank you for taking this on! I've participated in many discussion on this topic over the 20 or so years I've been on the internet and I have a few anecdotes to share from these discussion over the years.
Early on, the subject intrigued me so much that I called Bill Davis at Tioga Engineering to pose the question to him. He was very patient and indulgent in answering my query. He told me that he had never observed the phenomenon, but did not rule it out. I shared with him the viewpoint of the proponents (corkscrew path, bullet goes to sleep downrange) to which he replied that bullet swerve did exist, but it was very small, on the order of a fraction of a caliber. He immediately started reasoning through a way to empirically test the existence using an onion paper target at short range so as not to upset the path of the bullet as it continued downrange. (through the years, I proposed acoustic targets as even less disruptive as they became available). That he did not discount it entirely and was thinking of ways to test for the phenomenon impressed me. I was sad to only recently find out that he is no longer with us.
One of the anecdotes that is commonly brought up by the proponents of bullets going to sleep and causing smaller groups down range that at close range is the Gale McMillan experience testing 50 cal sniper rifles. Rather than recount his writings here, I'll see if I can find a link through the magic of the internet. In short, Mac observed in shooting thousands of rounds of 50 BMG that they grouped smaller at 1000 yds than at the shorter distances. (hence there might be value in tapping the 50 cal crowd to take up the challenge since sadly Mac is also no longer with us).
I personally find it hard to reason through how the many forces acting to disrupt a bullet's path can be magically reversed. I believe Harold Vaughn offered similar explanations of why people were observing this phenomenon (scope parallax and bad statistics) in his book.
There is one very specific case of the phenomenon that remains credible for me though. It was touched on by Zfastmalibu; Positive Compensation, which helped to explain dispersion in the vertical plane only. The history of positive compensation goes back to the British fullbore experience. In the early days, the ball ammo used for long range was terrible for ES, and the Enfields were quite "whippy". Some smart brit figured out you could harness the both to allow for the slower rounds to be released from the barrel at a higher point in the whip and the faster rounds at a lower point. The result was rounds that would converge for vertical at the desired range (typically 1000 yards). GE Fulton was reknown for tuning or "regulating" Enfields to produce this effect. There's a short article of this in the old NRA Highpower Series that I'm going to guess you already have, but that I will dig up and try to scan for the crowd here. It mentioned that compensation was also seen in M14's though in a lesser degree.
Lastly, I have a good friend and fellow service rifle competetor that swears his AR with 80's and 90's group tighter at 300 yards than at 100yds. We get along great otherwise, and even worked well together in sorting out the 90gr JLK's out of an AR Service Rifle (I ran the pressures on his loads to ensure the speed freak didn't blow himself up). I'm going to see if I can get him to take on your challenge.
Thanks for continuing to do the good work.
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Chris F, I know this isnt exaclty the place for It but I love the AR platform and would like to know if it would be ok to PM you and ask you a few things about your experience in the service rifle competitions, Id like to get the most out of my Match grade AR and any experience youre willing to share would be greatly appreciated.
When I started TR it was explained to me, it's easier to place a cup in the centre of plate than it is to put in the middle of a saucer. I don't know that the ratio of white:black aiming marks have really been explored, given a 300y aiming mark put up in error on a +800y frame is quickly brought to the attention of the butts officer.
Shooters will often use the same aiming mark when sighting in at all the short ranges, so I'm not surprised groups might start to tighten up with distance. For cross-hair optics, I prefer a diamond shaped aiming mark. I will frequently use a 500mFly target, especially with low and medium power scopes to verify groups at 200 and 300 y/m. The old adage, aim small miss small might be artificially induced when shooters keeps moving the same sized aiming mark further back, until the cross-hairs:aiming mark reaches some magical ratio like the white:black TR ratio?
Danehunter
Well-Known Member
Perhaps one method of testing the "sighting factor" of this reported phenomenon may be to shoot at 100 yards on, say 4 power, and at 300 yards at 12 power so that the "scope view" of the target appears to be approximately the same size at each distance.
If tested enough times this may show the same MOA dispersion rate and then discount the observed phenomenon of "tightening groups" at greater ranges. (or not...)
If tested enough times this may show the same MOA dispersion rate and then discount the observed phenomenon of "tightening groups" at greater ranges. (or not...)
