I used a Factory 24 or 28 incher I cant rember which, the problem with 1 gas port is sometimes the holes gets to big before you have the gas you need to function properly thats where having 2 medium holes comes in handy. I paid $30 for this used barrel and just hacked it off and re worked the muzzle in my Lathe. I drilled the holes with a plain drill press and vise (didnt have a mill a the time). Nothing to terribly hard, living 30 miles from anyone I just stepped out the shop and shot a few round and went back and opened the ports up alittle more ( a few thousands at a time) until the gun ran %100.
I have a thread over on silencertalk about building it. Remmington made a few factory 14 inch 1100s for their LE clients, but they didnt want to. Mine had 200-300 rds threw it and no issues yet.