Thread: Same load increased velocity 🤔

Originally Posted by Cordite

Amount of bolt thrust can have no discernable effect on muzzle velocity. The case / bolt are not moving backwards in any "equal & opposite" reaction, only the entire rifle is moving back. That said, a thought on equal and opposite reactions.. if you support an all-metal rifle against a solid immovable back-stop (not even a soft recoil pad) vs a human shoulder, will the MV be significantly higher and/or more consistent from backstop-supported shots?

So, had to do some calculations on this. A 174grain (11.28gram) projectile at 2450 fps through a 4kg all-metal rifle.

Rifle will recoil at 7.14 fps into the shoulder by time the projectile is at the muzzle, as an opposite reaction to the accelerating bullet proportional to their relative mass difference. Additional recoil as gases exit does not affect muzzle velocity.

The same rifle supported against an immovable, non-giving back stop will launch the same projectile at 2457 fps, turning the rifle into an impressive, long-range shooter... (<:

Basically the more powerful the cartridge and the lighter the rifle is, the greater relative differences in MV between supported butt vs. unsupported butt.