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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Bullet failure article
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<blockquote data-quote="CatShooter" data-source="post: 141302" data-attributes="member: 7"><p>[ QUOTE ]</p><p>I'd tend to disagree w/their assessment on groove #s and the effects they have. How about yall /ubbthreads/images/graemlins/confused.gif???</p><p></p><p>Here's the link in case that is a little too tough to read for you old codgers /ubbthreads/images/graemlins/grin.gif.</p><p></p><p><a href="http://www.benchrest.com/forums/showthread.php?t=40028" target="_blank">http://www.benchrest.com/forums/showthread.php?t=40028</a> </p><p></p><p>[/ QUOTE ]</p><p></p><p>Yup... me too.</p><p></p><p>Plus I disagree with their theory about barrel friction/lead melting.</p><p></p><p>If you consider the amount of time in the barrel (about 1.5/1000ths of a second), the thermal coefficient of jacket metal is not fast enough to melt the lead before the bullet is in free air.</p><p></p><p>Plus, given long barrels of the same length (I shoot a lot of 28" tubes), if a bullet is coming apart in a 10" twist barrel, it won't in a 12" barrel... and the friction/length/time in barrel" is the same.</p><p></p><p>Plus... if you are shooting a short barrel (20"), with a twist/velocity ratio that gives you the same spin, you find that the bullets still come apart, with 1/3 LESS friction.</p><p></p><p>Hmmmmmm??</p><p></p><p>I have been chasing this issue for about 25-30 years, and as I see it, it is simply a matter of jacket strength. My first blow ups were back in the 1970's a .220 Wilson Arrow, using 50gr and 55gr Hornady SX's that had 0.009" jackets.</p><p>They blew up at around 3,400 to 3,500fps.</p><p></p><p>The same design (50gr SP's) with 0.18" jackets could be driven out of the .220 Wilson Arrow at the speed of light without failure. Same barrel time, same velocity, same friction (actually more friction, because the 0.018" jacket had more resistance to rifling deformation... therefore more friction).</p><p></p><p>It is pretty well known that J4 jacket material is softer than the jackets made by Sierra and the others.</p><p></p><p>Berger is in a tough spot on this. They are now owned by J4 (IIRC), so they can't switch jackets, so they can't solve this problem, and the 1000yd bench shooters are bitching about the Bergers blowing up on the way to the target...</p><p></p><p>The ol' "Rock and a hard place"</p><p></p><p>.</p></blockquote><p></p>
[QUOTE="CatShooter, post: 141302, member: 7"] [ QUOTE ] I'd tend to disagree w/their assessment on groove #s and the effects they have. How about yall [img]/ubbthreads/images/graemlins/confused.gif[/img]??? Here's the link in case that is a little too tough to read for you old codgers [img]/ubbthreads/images/graemlins/grin.gif[/img]. [url="http://www.benchrest.com/forums/showthread.php?t=40028"]http://www.benchrest.com/forums/showthread.php?t=40028[/url] [/ QUOTE ] Yup... me too. Plus I disagree with their theory about barrel friction/lead melting. If you consider the amount of time in the barrel (about 1.5/1000ths of a second), the thermal coefficient of jacket metal is not fast enough to melt the lead before the bullet is in free air. Plus, given long barrels of the same length (I shoot a lot of 28" tubes), if a bullet is coming apart in a 10" twist barrel, it won't in a 12" barrel... and the friction/length/time in barrel" is the same. Plus... if you are shooting a short barrel (20"), with a twist/velocity ratio that gives you the same spin, you find that the bullets still come apart, with 1/3 LESS friction. Hmmmmmm?? I have been chasing this issue for about 25-30 years, and as I see it, it is simply a matter of jacket strength. My first blow ups were back in the 1970's a .220 Wilson Arrow, using 50gr and 55gr Hornady SX's that had 0.009" jackets. They blew up at around 3,400 to 3,500fps. The same design (50gr SP's) with 0.18" jackets could be driven out of the .220 Wilson Arrow at the speed of light without failure. Same barrel time, same velocity, same friction (actually more friction, because the 0.018" jacket had more resistance to rifling deformation... therefore more friction). It is pretty well known that J4 jacket material is softer than the jackets made by Sierra and the others. Berger is in a tough spot on this. They are now owned by J4 (IIRC), so they can't switch jackets, so they can't solve this problem, and the 1000yd bench shooters are bitching about the Bergers blowing up on the way to the target... The ol' "Rock and a hard place" . [/QUOTE]
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