Why Is A Mini-14 Louder Than An AR?

[Treo]

Please explain why a Mini-14 & an AR 15 (or an M-16 for that matter) sound so different when firing. & of course this is assuming identical loads.

 

[rcmodel]

Probably because the Mini-14 has a completely open receiver when the bolt opens, whereas the AR is completely enclosed, except for the ejection port.

Residual gas pressure pops out of the open receiver right by your ear on the Mini.
It is all directed away from you with an AR.

A second source of sound is from the Mini's gas piston releasing excess gas at relatively high pressure as it cycles.

The AR's operating gas is contained inside the bolt carrier until vented out the side, also away from you. By then, it is probably at a lower pressure & cooler then it is from the Mini's gas cylinder vent.

rcmodel

 

[lmccrock]

Also depends on the muzzle device - there is a greater variety of AR brakes and flash hiders than for Mini-14. My AR is quiet to me (relatively) but brutal to someone to the side and/or behind, due to the comp.

Lee

 

[Treo]

Ok that makes sense, thanks.

 

[Organdonor]

My AR and my Mini-14 both have no flash hiders nor muzzle brakes on the ends of the barrels. My Mini has a 16" barrel, the AR is 20"... the shorter the barrel, the more noise, too!

 

[ArmedBear]

Note that the Mini's gas port is just an L-shaped pipe that opens up within an inch of the barrel. The full pressure pulse blasts out of there, right under the holes in the handguard.

The AR has a long gas tube and the pressure comes out inside the upper receiver, with a longer but smaller pulse, I believe.

It may be also that the Mini opens the bolt a tad sooner than the AR, also for the reasons above.