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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Bullet RPM and performance
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<blockquote data-quote="BallisticsGuy" data-source="post: 2524456" data-attributes="member: 96226"><p>It's quite possible for rifling design, twist rate, RPM (which is an emergent effect of twist rate and velocity) to affect how a bullet performs in terms of terminal ballistics. It would be nonsensical to make a blanket statement that it does or does not affect terminal performance because details matter. As an example: One of my rifles in .223 caliber uses polygonal rifling with 1:7 twist rate. The polygonal rifling doesn't actually engrave the bullet but instead swages it. I can shoot a particular 45gr bullet out of that rifle and it's just fine and effectively converts squirrels into atmospheric gasses. If I take the same ammo and put it in another rifle of mine that has the same twist rate but has standard Enfield type rifling that does engrave the bullet, the bullets turn into a grey puff of smoke before they get to 25m out of the muzzle. The rifling design in one weakens the jackets on a bullet model with an intentionally weak jacket and the excessive spin (a 1:14 twist is perfectly sufficient at the velocities I'm pushing with them). The bullets are within spitting distance of 400,000rpm from a 1:7 twist barrel and they're really not designed for not much more than ~250,000rpm. I only get away with it in my polygonally rifled barrel because the jacket isn't substantially weakened by the swaging. From the conventionally rifled barrel the bullet jackets are substantially weakened, so much so that they expand from sheer radial velocity. So, if they even made it to a squirrel from that barrel they would be very expand-happy.</p></blockquote><p></p>
[QUOTE="BallisticsGuy, post: 2524456, member: 96226"] It's quite possible for rifling design, twist rate, RPM (which is an emergent effect of twist rate and velocity) to affect how a bullet performs in terms of terminal ballistics. It would be nonsensical to make a blanket statement that it does or does not affect terminal performance because details matter. As an example: One of my rifles in .223 caliber uses polygonal rifling with 1:7 twist rate. The polygonal rifling doesn't actually engrave the bullet but instead swages it. I can shoot a particular 45gr bullet out of that rifle and it's just fine and effectively converts squirrels into atmospheric gasses. If I take the same ammo and put it in another rifle of mine that has the same twist rate but has standard Enfield type rifling that does engrave the bullet, the bullets turn into a grey puff of smoke before they get to 25m out of the muzzle. The rifling design in one weakens the jackets on a bullet model with an intentionally weak jacket and the excessive spin (a 1:14 twist is perfectly sufficient at the velocities I'm pushing with them). The bullets are within spitting distance of 400,000rpm from a 1:7 twist barrel and they're really not designed for not much more than ~250,000rpm. I only get away with it in my polygonally rifled barrel because the jacket isn't substantially weakened by the swaging. From the conventionally rifled barrel the bullet jackets are substantially weakened, so much so that they expand from sheer radial velocity. So, if they even made it to a squirrel from that barrel they would be very expand-happy. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Bullet RPM and performance
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