11 inch barrel gas length?

[midnitesi]

I don't have a lot of experience ( a little with 556 and 300 blk) in shorter barrels, but would think your best choice would be carbine length.  Just 2 cents however. 

Look at how much barrel lies beyond the gas block to the muzzle, that's your dwell-time "length".  6Arc pressures being Saami limited to 52 ksi, vice the 556 or 300 Blk at (IIRC) 56 ksi, inch for inch the 6Arc should have a lower pressure than either; and gas volume right between those 2 via the bore size.  So I would vote for the carbine length.  I personally don't prefer shorter gas tube lengths b/c that means more back pressure to the bolt... and possibly  into my face, leakages from the chamber area I mean.

that is my normal way of thinking for dwell times etc. the kicker is im seeing 18, and 20 inch barrels with rifle +1 or +2 length gas tubes, and still running just fine, specially the 18 inch rifle +2 ones. which has me wondering if dwell times is not really much of an issue with 6arc.