What is the shortest barrel length can one use (from a reliability standpoint)for a SBR with a suppressor? I am considering a 4 1/2" in order to use any out of the box bulk ammo and not worry about supersonic rounds... I cannot buy standard velocity ammo in my town and have to order it off the internet.
Does anyone have any real life experience on this? Any input would be appreciated - thanks in advance...
PS - I am already a "stamp collector" and do not need lectures on the NFA regulations...
Mines at 6" and I use CCI standard velocity to be really quiet, bulk is quiet enough for me, there's not a huge difference in noise. The bolt will be the loudest part no matter what ammo you use.
These are blow-back and the only things keeping the bolt closed are the spring and mass of the bolt. Any barrel length will work in theory but you may need to twiddle the spring and bolt weights. Unfortunately S&W does not sell these parts to end users to my knowledge.
The M&P15-22 Pistol has a 6" barrel and looks like a good starting point. But getting those parts is doubtful as well.
Since having cut 10'' of the barrel I never messed with spings or anything and its run perfectly fine the last 2k rounds. Come to think I may have only had two dud rounds out of that.
If your gonna go that short you may need to lighten the bolt due to the lesser amount of gas pressure to send it back. Here are some differences between the pistol and rifle bolt.
SBR barrel length
Linear Mode
