I built mine with a Faxon Gunner 11.5", I like it and is shoots well suppressed and unsuppressed, granted itis fairly new so only a few hundred thru it so far.
I honestly am suprised that the first detractor mentioned about that barrel wasn't that it has a midlength gas system.
as for a few dollars more, I paid 100 less than a BCM, I am usually a BCM whore, and just about half of what a DD barrel would have cost me. Are they better, most definitely, but so far it seems to be a decent barrel for the money.
You do have to bear in mind that if you go with the Faxon Gunner that unless Brownells has the Carbine gassed one(their exclusive if I recall) you are stuck with a Midlength which might be finicky with function. Mine works well with a H2 buffer and also works like a champ with a VLTOR A5 system using a A5H2 buffer, shot Tula suppressed, Sico Hybrid ejection about 4-5, and unsuppressed, ejection about 3. It was a bit gassy with American Eagle, but not bad, more smell than feeling gas on my face.
As for the Gas, as stated before .625 gas block, but because it is a 11.5" mid it has I think a .090" port, they suggest a adjustable gas block, but I can attest it seems to run just fine without one. I chose not to use one, due to the rail I am using not playing well with midlength gas systems, have to remove material from the gas block to clear the built in front sight in the rail, and I am not one to remove material that may cause the product to not work properly
Edit: Gas port on the Gunner is .110"