I'm in the planning phases of my next build and was curious as to what bore diameter the 7.62x39 barrels as offered by DPMS, M-A Parts, etc.

Are they .308cal or .311cal barrels?

I know the .311cal bullet of the 7.62x39 will go through a .308cal barrel with no issues, but am curious for the purposes of reloading (better bullet availability in .308). While .311 is fine in the .308cal barrel, accuracy-wise the .308bullets may not be so well in the .311 cal barrels.  
I ask because I'm thinking of something subsonic a'la .300 whisper but with better brass availability-plus the use of AK mags in the new MGI lower.

My DPMS barrel was marked .310