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Posted: 10/4/2010 8:22:20 AM EDT
| I loaded up some 75 grain Hornady HPBT rounds. However, I am shooting them fron a 1:9 20" barrel. I am wondering if it will stabilize these heavy/long bullets. How do I tell if they are being stabilized or not? I shot a few of them yesterday and they seemed OK, holes in the paper were perfect circles and not different than the 55 grain holes. If they aren't being stabilized will they keyhole? Or will i just shoot big groups? Also, I was only shooting at 100 yards, will I have to shoot longer distances to know if they are stabilizing or not? |
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The holes were round. The bullets are stable.
It's possible you might load some up at very low speeds, then find out they slow so much at long ranges that they become unstable. I wouldn't worry about it. A bullet that is transitioning from just barely stable to tumbling flight will start describing a helix along its trajectory, but your target would need to be at exactly the right distance to pick up the increase in group size, and it would need to be close in my experience. The only times I've shot badly unstable bullets the helix was so large that the target was in no danger of a bullet strike. I've watched high power rifle loads through my spotting scope that were wild and the impact was completely unpredictable. |
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Quoted:
The holes were round. The bullets are stable. It's possible you might load some up at very low speeds, then find out they slow so much at long ranges that they become unstable. I wouldn't worry about it. A bullet that is transitioning from just barely stable to tumbling flight will start describing a helix along its trajectory, but your target would need to be at exactly the right distance to pick up the increase in group size, and it would need to be close in my experience. The only times I've shot badly unstable bullets the helix was so large that the target was in no danger of a bullet strike. I've watched high power rifle loads through my spotting scope that were wild and the impact was completely unpredictable. Low charge rounds is a good idea. How low owuld you go? I was using 23 grains of Varget for these at 100 yards, would you knock 1/3 off for a 300 yard representation? Or is there not a direct correlation like that? I guess I could chrono some low powered rounds and try to find a velocity that would match 300 yards or so. |
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Quoted:
Quoted:
The holes were round. The bullets are stable. It's possible you might load some up at very low speeds, then find out they slow so much at long ranges that they become unstable. I wouldn't worry about it. A bullet that is transitioning from just barely stable to tumbling flight will start describing a helix along its trajectory, but your target would need to be at exactly the right distance to pick up the increase in group size, and it would need to be close in my experience. The only times I've shot badly unstable bullets the helix was so large that the target was in no danger of a bullet strike. I've watched high power rifle loads through my spotting scope that were wild and the impact was completely unpredictable. Low charge rounds is a good idea. How low owuld you go? I was using 23 grains of Varget for these at 100 yards, would you knock 1/3 off for a 300 yard representation? Or is there not a direct correlation like that? I guess I could chrono some low powered rounds and try to find a velocity that would match 300 yards or so. No, do not cut your powder charges by 1/3!!!! You best option is to shoot these out to 300 and check the target. Usually a 20" 1:9 barrel will stabilize 75's with no issues, especially if you keep the velocity high. The longerAmax or any other long bullets are iffy. I have seen 75 grain loads loaded to both SAAMI and NATO spec keyhole out of 1:9 carbine barrels. Put any 75 grain bullet in a 1:9 24" space gun or bolt gun barrel and they'll usually shoot just fine. A 1:9 barrel was fine up to about 1993 when the heaviest bullet made was a 69 Sierra Matchking. Today's heavier bullets simply need a 1:8 or 1:7 to be sure. |
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Quoted: Quoted: The holes were round. The bullets are stable. It's possible you might load some up at very low speeds, then find out they slow so much at long ranges that they become unstable. I wouldn't worry about it. A bullet that is transitioning from just barely stable to tumbling flight will start describing a helix along its trajectory, but your target would need to be at exactly the right distance to pick up the increase in group size, and it would need to be close in my experience. The only times I've shot badly unstable bullets the helix was so large that the target was in no danger of a bullet strike. I've watched high power rifle loads through my spotting scope that were wild and the impact was completely unpredictable. Low charge rounds is a good idea. How low owuld you go? I was using 23 grains of Varget for these at 100 yards, would you knock 1/3 off for a 300 yard representation? Or is there not a direct correlation like that? I guess I could chrono some low powered rounds and try to find a velocity that would match 300 yards or so. You seem to misunderstand. A stable bullet will make nice, round holes in paper targets. An unstable bullet will keyhole (it tumbles), if you're lucky enough to hit paper. The faster you push the bullet, the MORE stable it will be. As the bullet slows, it will become LESS stable. At some point, the bullet will tumble like a knuckleball. My nephew's 1-9 16" barrel stabilizes 75 gr. bullets out to about 300 yds. His is accurate out to there (less than MOA). After 300, the bullets can't find the target at all. As in, 12+ MOA. Not really sure, because at 400 yds., we can't hit paper at all. Nothing. In your rifle, they may well be OK at short ranges, but at long distances may tumble. The only way you will know if they will work in your rifle, is to try them. |
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