Rosco Manufacturing PB-16-HB-300BLK-8-P Purebred 300 Blackout 16″ Nickel Boron Stainless Steel Barrel
CMMG 30D120A Barrel Sub-Assembly 300 Blackout 16.10″ Black Nitride Finish 4140 Chromoly Steel Material Carbine Length with Medium Taper Profile for AR-15
CMMG 22D7C4A Replacement Barrel Kit with Collar, 22 LR 16.10″ Threaded, Black Nitride Chromoly Steel, Fits AR-15/Mk4