I’m trying to decide what barrel length would be optimal for my SBR build.
The gun will be my home defense rifle, but I would also like to to be effective at the range out to 75-100 yards or so. What do you guys think? I’m just going to have my current M4 barrel cut down by ADCO. I’m running a CAR gas system.
No shorter than 10.3" - I prefer an 11.5" myself.
I like the 12.5" Operator barrel from Dennysguns/GTS.
“10-13” will work nicely for you.
HTH
This is the range to go for. Any longer IMHO isn’t worth the $200 and registration. Any shorter than 10" will usually result in function issues, and certainly result in severe velocity loss. The fireball and blast are fun though…unless you’re the guy next to you :D. I think the best compromise is 11.5". Of course, our advice would be to get a 10, 11.5 and a 12.5…maybe (2) 11.5"
I vote 11.5… It should do what you want.
I held one the other day and it was real short and maneuverable… very nice indeed!
11.5
I have 2 of those in my weapon stash.
At least 10.5 to stay alive!
Cameron
11.5
10.5 is theoretically less reliable, although real world reliability is fine.
10.5 is harsher on silencers.
I would suggest on either 11.5" or 12.5". You wont loose a lot of velocity compared to a 16".
Going lower than 10.5" sometimes gets a little finicky when troubleshooting on a Failed to Extract, Failed to Cycle or Failed to Feed. This is what happened to me with my 7.5"
G-luck. I hope your project goes well 
I really like the look of the 10.5" barrels. As far as reliability with a DI CAR gas sytem, what’s the consensus? Is a 10.5" SBR one application where a piston conversion actually makes sense?
IMO no. A piston gun only “makes sense” under a certain set of circumstances, and simply running a 10.5" barrel isn’t enough justification.
Ok thanks for the input. Do you think the gas port may need to be opened up a bit? I’m having a 14.5" cut to 10.5" once the stamp comes back.
RIGHT! When the gun is an AK. 
lol1!!1
One thing that isn’t quite clear to a lot of people is that suppressed AKs get real dirty and it would behoove the end-user to keep them well lubed.
OMGZ!11! :eek:
My 10.5" LMT DI has never jammed, and I’ve shot all types of ammo through it. You don’t even need to do the H (H2, H3, etc.) Buffer thing. Functions perfectly w/ a carbine buffer. No bounce, no jams, no problems. As long as you stay with a quality build, which is worth every penny, you’ll be more than fine w/ a DI 10.5". Stick w/ LMT or Noveske.
**Also get a quality BCG (again, worth every penny).
Have Fun!!
I’d buy a factory 10.5" barrel instead. What you want to do is too much fooling around.
This gun should have atleast have an H buffer.
Seems like a waste of money . . . . 
Why? Having a barrel chopped introduces a lot more risks and chances for damage than a factory LMT or Noveske barrel. The gas port will be tuned correctly, the chrome lining won’t have the possibility of being damaged in the chop, and you usually will have factory warranty support if something doesn’t work right (which often does not).
NFA is not a poor man’s game. You have to pay to play.