Semiauto rifles and energy?

[smiljko]

I went into an argument with my friends and the question is are semiauto rifles losing energy due to gasses used to operate the action? If so, how much 1,3,5,10% ??
We don't have the chrono to perform the test(bolt vs semiauto),but someone must have done it.

Thanks

[Scorch]

Theoretically, yes, because bleeding gas from the bore takes energy to operate the bolt mechanism away from propelling the projectile.

In practical application, no, because it takes such a small volume of gas to operate the bolt, and there is so much residual pressure inside the bore when the bullet leaves the bore (that's what makes the gun go BANG). For all practical purposes, there is no discernible loss of power due to bleeding off pressure to operate the bolt assembly.

I have seen numerous tests trying to determine power loss from autoloaders, and all come to the same conclusion. Generally, velocity loss is less than 1%, well within the variation between two different lots of ammo. When you graph the deviation between the control and the test rifles, you will find considerable overlap of the two graphs.

[smiljko]

Thanks Scorch for clearing that up for me!

[5whiskey]

There is one difference... felt recoil.

[williamd]

I wondered about this before. Took gas semi and bolt rifles with same bbl lengths, used same loads and shot across my Chrono. Velocities overlapped. Sure there are more variables but I was satisfied the semi was not 'penalizing' me. Did it with shotguns, too.

Do not let anyone use your chronograph with a shotgun w/o a deposit. Even at 10 ft there is some spread! So, gotta be a bit careful. On the other hand, got my Chrono replaced! :D .

[smiljko]

Another myth broken :) , and I won a bet :D !