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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
revolutions per minute debate
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<blockquote data-quote="4ked Horn" data-source="post: 69244" data-attributes="member: 11"><p>OK I am back to your original questions. I don't know what conflicting info you found but the correct answers seem clear and generally understood by most people responding. </p><p> </p><p>[ QUOTE ]</p><p> If a bullet leaves a barrel that has a 1-8" twist, is it still spinning 1 time in every 8" all the way through it trajectory say out to 1000 yards? </p><p></p><p>[/ QUOTE ] </p><p></p><p>It will be spinning at a faster "Rotation Per Distance". If your MOAG puts a bullet at 2k in 3 seconds there will be almost 0 spin decay. The RPMs we are talking about here are rediculous fast. I have seen video of a steel ball bearing spinning at one million RPM in a magnetic bearing. It is indestinguishable from a stationary steel ball. If left to settle on its own it would take days to stop. If the bullet is going 360,00 RPM at the muzzle it is probably going 359,999.9 RPM at 2k. However your bullet is slowing its FPS. This means the bullet RPD will be increasing to 1:7 then 1:6 then 1:5 and so on. If your 2k velocity is half of your MV then the twist ratio is (really really) close to double (1:4).</p><p></p><p> [ QUOTE ]</p><p> If you were to shoot a 55 grain bullet out of an 8 twist barrel at 4000 fps, and then shoot a 80 grain bullet out of the same barrel at 3000 fps, they have different rpm's, but do they both still spin 1 time every 8 inches? </p><p></p><p>[/ QUOTE ] </p><p></p><p>If the barrel they are leaving is wearing a 1:8 rifling how CAN'T they. But he moment they leave contact with the muzzle they adopt their own velocity decay and in turn the paragraph you just read applies to them at different magnitudes.</p><p></p><p>Clear as a bell. /ubbthreads/images/graemlins/laugh.gif</p></blockquote><p></p>
[QUOTE="4ked Horn, post: 69244, member: 11"] OK I am back to your original questions. I don't know what conflicting info you found but the correct answers seem clear and generally understood by most people responding. [ QUOTE ] If a bullet leaves a barrel that has a 1-8" twist, is it still spinning 1 time in every 8" all the way through it trajectory say out to 1000 yards? [/ QUOTE ] It will be spinning at a faster "Rotation Per Distance". If your MOAG puts a bullet at 2k in 3 seconds there will be almost 0 spin decay. The RPMs we are talking about here are rediculous fast. I have seen video of a steel ball bearing spinning at one million RPM in a magnetic bearing. It is indestinguishable from a stationary steel ball. If left to settle on its own it would take days to stop. If the bullet is going 360,00 RPM at the muzzle it is probably going 359,999.9 RPM at 2k. However your bullet is slowing its FPS. This means the bullet RPD will be increasing to 1:7 then 1:6 then 1:5 and so on. If your 2k velocity is half of your MV then the twist ratio is (really really) close to double (1:4). [ QUOTE ] If you were to shoot a 55 grain bullet out of an 8 twist barrel at 4000 fps, and then shoot a 80 grain bullet out of the same barrel at 3000 fps, they have different rpm's, but do they both still spin 1 time every 8 inches? [/ QUOTE ] If the barrel they are leaving is wearing a 1:8 rifling how CAN'T they. But he moment they leave contact with the muzzle they adopt their own velocity decay and in turn the paragraph you just read applies to them at different magnitudes. Clear as a bell. [img]/ubbthreads/images/graemlins/laugh.gif[/img] [/QUOTE]
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revolutions per minute debate
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