Barrels

AR-15 and AR-10 barrels from Ballistic Advantage and Faxon in 5.56, .223 Wylde, .300 Blackout, .308 and 6.5 Creedmoor, from 7.5 inch pistol lengths to 20 inch rifle barrels, plus Glock replacement and threaded barrels. Chrome-lined, nitrided and stainless, in government, pencil and heavy profiles.
Ships to your door, no FFL. Twist rate is the number to check: 1:7 or 1:8 stabilizes the heavier 5.56 bullets, 1:9 is fine for 55 grain and lighter. Gas system length has to match your handguard and gas block, so pick the barrel first and build out from it.