Hey... long rangers... got a bullet / predictability question... - Page 2

Hummer70 · November 16, 2014, 10:24 AM

First off Bart and I have shot the same matches at the same time but never knew each other and we both have seen elongated holes more times than we care to remember with 168s at 1000 yards. What makes it worse is we both know/knew the same people which has in all probability ruined both our reputations haha.

I had a interesting experience/observation in the 86 Palma Match with the 168s. I got squadded with a Gunny I had never met so we started shooting and I caught my favorite relay for the Palma (1st) and I observed he was doing well with the stick and I had a 30.06 Mod 70.

We went to the pits and of course after 800 his holes were round but that afternoon we shot the 900 and 1000 and went to the pits. I had a good score that I thought would be beat and the Gunny had a good score as well and wasn't far behind me score wise.

In the pits guys were reporting their scores and my hopes raised a bit and after firing was completed we got on the carts for the ride to the line and Mid Tompkins was on the other side of cart and asked me how many I was down and I told him and he said, "That is the best I have heard." But as Bart and I both know when they squad the Palma the High Masters are squadded by the luck of the card they hand you.

We both fired the 900 and 1000 and went to the pits and though his holes were elongated he still had a good score so we started talking and we started talking about 168s yawing and he said in their mount testing at Quantico they had come to the conclusion that the transition did not affect their accuracy that much so they stayed with 168s and since his score was very close to mine I could not challenge the evidence.

I got back to the firing line and was going to get my cart/gear and ran into George Tubb who was taking up score cards and he looked at me and smiled and said, "Looks like you got it again." I had won the Palma Match the previous year with same rifle/load. But the surprise was yet to come.
At the award ceremony they make awards for high bolt gun and high service rifle and to both our surprises he won high service rifle catagory and they called out the bolt gun winner and George was right, I had taken it again.
Talk about odds, what the odds of two guys that never met, getting squadded together on the same point and both of us winning our separate catagories.

At that time I was the only person to ever win the Palma two times, now it appears eight others are on the list but with several years separations between their wins. There are two morals to this thread, first is elongated bullets can still give you a good score and once you hit a certain level in long range competition it is not guarantee you will win every time because if you are shooting when you are supposed to scratching and/or scratching when you should have been shooting makes the difference between being on top that day or near the top.

Bart B. · November 16, 2014, 10:31 AM

Jimro, thanks for posting that link to some very interesting stuff. I plan to go through it more than my quick glance did, but I noticed one interesting thing.

They used reduced charges of IMR4198 for lower muzzle velocities to "duplicate" down range in-flight behaviour of all three bullets. From what I've gleaned from several sources, bullet spin rate drops 10% to 15% from its rpm number at the muzzle to what it is going through the target at 1000 yards. If Mach 1 is 1125 fps, a bullet leaving at Mach 2.219 from a 1:12 twist barrel will spin 149,782.5 rpm. From a 1:10 twist barrel, it's rpm number goes up to 179,739 rpm. The same bullet leaving at Mach .703 will spin a bit over 3/10ths as fast; 47,452.5 rpm from a 1:12 twist and 56,943 rpm from a 1:10.

Those slow bullet launch velocities, to me, mean their spin rate at the velocity they'll have way down range are much lower than normally fired bullets will have. Would that change the results?

Jimro · November 16, 2014, 12:54 PM

Bart B.,

That's a good observation, and I think that the lower spin doesn't matter in this case because the spark diagrams are looking at "laminar flow" (except the projectile is moving, not the fluid) interactions.

The reduced reduced spin wouldn't change the spark diagrams that give you a look at the aerodynamic interactions. For all intents and purposes spin is simply the stabilizing factor that allows a bullet to nose into the wind, a slower spin simply means more precession yaw earlier in the flight.

Since we know that yaw precession grows as velocity drops and rpms decrease, the pictures of the bullets as is is a good indication of what projectiles at full distance are dealing with in terms of aerodynamics across the surface of the projectile. As long as there is enough spin for stability, the pictures are indicative of aerodynamics.

Jimro

Bart B. · November 16, 2014, 01:18 PM

Hummer70's comment about when one shoots while on the line with other equally ranked competitors separates the best scores from the darned near the best.

Best example of that to me was in the 1993 Rocky Mountain Palma Matches at Raton. In the last of 4 days of those long range matches, I was ahead of those just below me by several points shooting the final match stage. At 1000 yards with the high masters on the line, half way through it, a big wind gust suprised everyone. Depending on when you shot, the 155's were blown different distances to the left. Those that shot ahead of that gust had bullet holes on paper anywhere from 10 inches to 36 inches left of center and stayed on paper in the scoring rings and those at the edge were scored 6 points. Those who shot when it hit had their bullets go more than 36 inches from center; off the paper and were scored a miss; 10 points down. I finished third over all with a miss losing 10 points as did several others. Mid and Nancy Tompins finished ahead of me by 2 and 3 points respectively; they shot ahead of that gust. Had I been at the edge of the paper, I would have been 6 points higher and ahead of them by a few points.

There's some luck involved in all the shooting sports. Which is why the NRA changed the firing point assignments on the 1000-yard Viale Range at Camp Perry. The first 20 some odd firing points on the west side next to the tree line had scores fired on them typically higher than those at points 21 through 99 further east. It was a reason to level the playing field that all thought was a good thing to do.

November 16, 2014, 10:24 AM	#26
Hummer70 Senior Member Join Date: June 22, 2009 Location: South Carolina Posts: 203	First off Bart and I have shot the same matches at the same time but never knew each other and we both have seen elongated holes more times than we care to remember with 168s at 1000 yards. What makes it worse is we both know/knew the same people which has in all probability ruined both our reputations haha. I had a interesting experience/observation in the 86 Palma Match with the 168s. I got squadded with a Gunny I had never met so we started shooting and I caught my favorite relay for the Palma (1st) and I observed he was doing well with the stick and I had a 30.06 Mod 70. We went to the pits and of course after 800 his holes were round but that afternoon we shot the 900 and 1000 and went to the pits. I had a good score that I thought would be beat and the Gunny had a good score as well and wasn't far behind me score wise. In the pits guys were reporting their scores and my hopes raised a bit and after firing was completed we got on the carts for the ride to the line and Mid Tompkins was on the other side of cart and asked me how many I was down and I told him and he said, "That is the best I have heard." But as Bart and I both know when they squad the Palma the High Masters are squadded by the luck of the card they hand you. We both fired the 900 and 1000 and went to the pits and though his holes were elongated he still had a good score so we started talking and we started talking about 168s yawing and he said in their mount testing at Quantico they had come to the conclusion that the transition did not affect their accuracy that much so they stayed with 168s and since his score was very close to mine I could not challenge the evidence. I got back to the firing line and was going to get my cart/gear and ran into George Tubb who was taking up score cards and he looked at me and smiled and said, "Looks like you got it again." I had won the Palma Match the previous year with same rifle/load. But the surprise was yet to come. At the award ceremony they make awards for high bolt gun and high service rifle and to both our surprises he won high service rifle catagory and they called out the bolt gun winner and George was right, I had taken it again. Talk about odds, what the odds of two guys that never met, getting squadded together on the same point and both of us winning our separate catagories. At that time I was the only person to ever win the Palma two times, now it appears eight others are on the list but with several years separations between their wins. There are two morals to this thread, first is elongated bullets can still give you a good score and once you hit a certain level in long range competition it is not guarantee you will win every time because if you are shooting when you are supposed to scratching and/or scratching when you should have been shooting makes the difference between being on top that day or near the top. __________________ Distinguished Rifleman High Power & Smallbore Prone President's Hundred (Rifle) US Palma Teams(2) US Dewar Team (2),4 Man Natl.Champ Team SB Prone Cert Test Dir. Sm Arms and Ammo,Aberdeen Pr Ground, Firefighter I, AC4HT Last edited by Hummer70; November 16, 2014 at 10:45 AM.

November 16, 2014, 12:54 PM	#28
Jimro Senior Member Join Date: October 18, 2006 Posts: 7,097	Bart B., That's a good observation, and I think that the lower spin doesn't matter in this case because the spark diagrams are looking at "laminar flow" (except the projectile is moving, not the fluid) interactions. The reduced reduced spin wouldn't change the spark diagrams that give you a look at the aerodynamic interactions. For all intents and purposes spin is simply the stabilizing factor that allows a bullet to nose into the wind, a slower spin simply means more precession yaw earlier in the flight. Since we know that yaw precession grows as velocity drops and rpms decrease, the pictures of the bullets as is is a good indication of what projectiles at full distance are dealing with in terms of aerodynamics across the surface of the projectile. As long as there is enough spin for stability, the pictures are indicative of aerodynamics. Jimro __________________ Machine guns are awesome until you have to carry one.

November 16, 2014, 10:31 AM	#27
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	Jimro, thanks for posting that link to some very interesting stuff. I plan to go through it more than my quick glance did, but I noticed one interesting thing. They used reduced charges of IMR4198 for lower muzzle velocities to "duplicate" down range in-flight behaviour of all three bullets. From what I've gleaned from several sources, bullet spin rate drops 10% to 15% from its rpm number at the muzzle to what it is going through the target at 1000 yards. If Mach 1 is 1125 fps, a bullet leaving at Mach 2.219 from a 1:12 twist barrel will spin 149,782.5 rpm. From a 1:10 twist barrel, it's rpm number goes up to 179,739 rpm. The same bullet leaving at Mach .703 will spin a bit over 3/10ths as fast; 47,452.5 rpm from a 1:12 twist and 56,943 rpm from a 1:10. Those slow bullet launch velocities, to me, mean their spin rate at the velocity they'll have way down range are much lower than normally fired bullets will have. Would that change the results?

November 16, 2014, 01:18 PM	#29
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	Hummer70's comment about when one shoots while on the line with other equally ranked competitors separates the best scores from the darned near the best. Best example of that to me was in the 1993 Rocky Mountain Palma Matches at Raton. In the last of 4 days of those long range matches, I was ahead of those just below me by several points shooting the final match stage. At 1000 yards with the high masters on the line, half way through it, a big wind gust suprised everyone. Depending on when you shot, the 155's were blown different distances to the left. Those that shot ahead of that gust had bullet holes on paper anywhere from 10 inches to 36 inches left of center and stayed on paper in the scoring rings and those at the edge were scored 6 points. Those who shot when it hit had their bullets go more than 36 inches from center; off the paper and were scored a miss; 10 points down. I finished third over all with a miss losing 10 points as did several others. Mid and Nancy Tompins finished ahead of me by 2 and 3 points respectively; they shot ahead of that gust. Had I been at the edge of the paper, I would have been 6 points higher and ahead of them by a few points. There's some luck involved in all the shooting sports. Which is why the NRA changed the firing point assignments on the 1000-yard Viale Range at Camp Perry. The first 20 some odd firing points on the west side next to the tree line had scores fired on them typically higher than those at points 21 through 99 further east. It was a reason to level the playing field that all thought was a good thing to do.