What would be the optimal barrel length for a suppressed rifle?
I run 12.7’’ and am very satisfied with dB reduction. Just wondering if it can be more.
Longer barrels will suppress better, all things equal. However, many silencers are optimized for shorter barrels, since very few folks put a silencer on a 20 inch M16A2.
I have one on a 20 inch and had one on a 10.5 pistol. There is a noticable difference, but the 10.5 sounded quieter to me. I guess because the bullet was going about 900 fps slower than in the 20 inch???
“Best” is kind of hard to determine, because your criteria may be much different than any other user.
The longer the barrel in a 5.56, the easier the shots will be on the first baffle of the suppressor, so longevity with theoretically be increased. It should, also in theory, be a little quieter the longer the barrel.
That being said, if you are an SBR nut like me you’ll want something as short as possible that is still reliable. I like my Noveske 10.5" SS using an older M4-2000.
I’m an SBR nut, too. But 12.7’’ is really the best of both worlds. 
I would do 10.5 but it’s just too short, and a bit too loud.
Yep, so best becomes way too much of a gray area. The reason I don’t like the longer barrels like 14.5 or 16 is because with the added length of the can, it becomes very cumbersome to me.
11.5 and 12.5 are probably fine shorter cans like the new M4-2000 or Surefire K cans.
Best?
for sound and suppressor life it’s a 16, 18, or 20"
For size/mobility it’s a 10.5"
For size/mobility/sound compromise and NO $200 tax, it’s a 14.5" with perm mount
For IMHO best mix of all traits, it’s a 12.5"
YMMV
Most 5.56 cans run between 6-7 inches, so a 10.5" is about as long at an M4, an M4 with a 6" can is about as long as a 20" M16.
For sound suppression coupled with ballistic performance - 18" is my choice (and as such, I have one)
For a mix of mobility and size with reflex suppressors - 11.5" is my choice (building that one)
In less enlightened states, the 14.5 or 14.7 Perm are hard to beat. (I’ve also got a 14.7" with pinned suppressor mount).
I think there’s a reason 11.5-12.5" are the most popular double stamp units.
I think I’ll stick with my 12.7’’ as a primary option now. Thanks guys.