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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
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<blockquote data-quote="Bart B" data-source="post: 1157258" data-attributes="member: 5302"><p>My 32" Palma rifle barrel in 308 Win shot 155's over 46 grains of IMR4895 at 3090 fps. Same ammo in a 26" barrel left at 2870(?) or thereabouts. 32" barrel was a few ten-thousandths smaller in groove and bore diameters.</p><p></p><p>Check page 22 for velocity versus barrel lengths data from SAAMI's info below:</p><p></p><p><a href="http://saami.org/specifications_and_information/publications/download/206.pdf" target="_blank">http://saami.org/specifications_and_information/publications/download/206.pdf</a></p><p></p><p>Interesting information on barrel length/velocity and bullet accuracy:</p><p></p><p><a href="http://www.thetruthaboutguns.com/2013/10/daniel-zimmerman/the-truth-about-barrel-length-muzzle-velocity-and-accuracy/" target="_blank">http://www.thetruthaboutguns.com/2013/10/daniel-zimmerman/the-truth-about-barrel-length-muzzle-velocity-and-accuracy/</a></p><p></p><p>Here's data for the .308 Win cutting off a barrel a few times then testing it at each length:</p><p></p><p><a href="http://bulletin.accurateshooter.com/2015/06/308-win-barrel-cut-down-test-velocity-vs-barrel-length/" target="_blank">http://bulletin.accurateshooter.com/2015/06/308-win-barrel-cut-down-test-velocity-vs-barrel-length/</a></p><p></p><p>Check out "Similar Posts" section in the above link; very interesting.</p><p></p><p>'Tis my opinion that good velocity data for a given cartridge and load across different barrel lengths is only meaningful when a single, very long barrel is cut off an inch at a time then tested in a fixed hard mount so human variables are eliminated. That's how SAAMI conducted their tests. As I've said before, average muzzle velocity with the same rifle and ammo can vary up to 100 fps across several folks hand holding it against their shoulder as they shoot it atop a bench. I've seen a 65 fps spread; others more.</p><p></p><p>Different bore, groove and chamber dimensions, as well as primers and how they're struck, also cause muzzle velocity spreads.</p></blockquote><p></p>
[QUOTE="Bart B, post: 1157258, member: 5302"] My 32" Palma rifle barrel in 308 Win shot 155's over 46 grains of IMR4895 at 3090 fps. Same ammo in a 26" barrel left at 2870(?) or thereabouts. 32" barrel was a few ten-thousandths smaller in groove and bore diameters. Check page 22 for velocity versus barrel lengths data from SAAMI's info below: [url]http://saami.org/specifications_and_information/publications/download/206.pdf[/url] Interesting information on barrel length/velocity and bullet accuracy: [url]http://www.thetruthaboutguns.com/2013/10/daniel-zimmerman/the-truth-about-barrel-length-muzzle-velocity-and-accuracy/[/url] Here's data for the .308 Win cutting off a barrel a few times then testing it at each length: [url]http://bulletin.accurateshooter.com/2015/06/308-win-barrel-cut-down-test-velocity-vs-barrel-length/[/url] Check out "Similar Posts" section in the above link; very interesting. 'Tis my opinion that good velocity data for a given cartridge and load across different barrel lengths is only meaningful when a single, very long barrel is cut off an inch at a time then tested in a fixed hard mount so human variables are eliminated. That's how SAAMI conducted their tests. As I've said before, average muzzle velocity with the same rifle and ammo can vary up to 100 fps across several folks hand holding it against their shoulder as they shoot it atop a bench. I've seen a 65 fps spread; others more. Different bore, groove and chamber dimensions, as well as primers and how they're struck, also cause muzzle velocity spreads. [/QUOTE]
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