Semiauto rifles and energy?

smiljko · March 28, 2007, 02:01 AM

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 · March 28, 2007, 11:15 AM

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 · March 29, 2007, 12:49 AM

Thanks Scorch for clearing that up for me!

5whiskey · March 29, 2007, 01:38 AM

There is one difference... felt recoil.

williamd · March 29, 2007, 12:00 PM

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!

.

smiljko · April 2, 2007, 05:30 AM

Another myth broken

, and I won a bet

!

March 28, 2007, 02:01 AM	#1
smiljko Member Join Date: April 16, 2005 Location: Croatia Posts: 85	Semiauto rifles and energy? 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

March 28, 2007, 11:15 AM	#2
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	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. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

March 29, 2007, 12:00 PM	#5
williamd Senior Member Join Date: March 13, 2007 Location: SoCal Posts: 801	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! . __________________ "Outlaw guns and only outlaws will have guns!" Unfortunately, we may be moving in that direction. NRA Benefactor, Conservative!, VN '64-'65. Never sell a gun or a car ... and retire rich!

March 29, 2007, 12:49 AM	#3
smiljko Member Join Date: April 16, 2005 Location: Croatia Posts: 85	Thanks Scorch for clearing that up for me!

March 29, 2007, 01:38 AM	#4
5whiskey Senior Member Join Date: October 23, 2005 Location: US Posts: 3,652	There is one difference... felt recoil.

April 2, 2007, 05:30 AM	#6
smiljko Member Join Date: April 16, 2005 Location: Croatia Posts: 85	Another myth broken , and I won a bet !