What is the effect of ....
...The length of the barrel of the .45 ACP (Five inches for the .45 Auto) which achieves 900 FPS in comparison with the barrel length of the 58 Remington (7.5 to 8 inches)?
Bullet accelerates for a longer period of time in the longer barrel. Therefore to achieve the same speed, less pressure is required.
My 5.5 inch Remington won't push a round ball (154 gr) to 900 FPS. IIRC it tops out about 650.
I can get close to 900 in my 5.5 inch Vaquero (200 gr .45 long colt with as much powder as I can stuff into it - about 35 to 40 grains.) but that has the additional variation of the crimp on the case.
I think the way that works in smokeless powder is, Crimp it heavy - increase the speed, crimp it light, decrease the speed. IIUC, the crimp permits pressure to build up before the bullet begins to accelerate. More crimp equals more pressure build up and hence, faster acceleration in the barrel.
In the Remington, what you have holding the ball in place is the tightness of the fit of the bullet in the chamber. That might be followed by a build up of pressure as the ball transitions from the chamber to the forcing cone.
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Last edited by Doc Hoy; February 3, 2013 at 09:37 AM.