Faxon Firearms Duty Series AR-15 5.56 Nato 10.5in Upper Receiver Socom Carbine Length 1-8 Twist 1/2x28 w/BCG Supressor Black. 5in SOCOM Profile 5.56 NATO barrel blends compact handling with improved dwell and gas timing from a carbine-length system. Machined from certified 4150 CMV button-rifled with a 1:8 twist and finished inside and out with durable black nitride this 10.5in SOCOM barrel is built for reliability heat resistance and consistent accuracy in duty and tactical carbines. Specifications for Faxon Firearms Duty Series AR-15 5.56 Nato 10.5in Upper Receiver: Manufacturer: Faxon Firearms Caliber: 5.56x45mm NATO Overall Length: 19.75 in Barrel Length: 10.5 in Barrel Profile: SOCOM Barrel Twist Rate: 1-8 Firearms Threads Per Inch: 1/2x28 Color: Black Gun Model: AR-15 Fabric/Material: Stainless Steel Handguard Length: 9 in Gun Make: AR Platform Flutes: No Package Contents: Faxon Firearms Duty Series AR-15 5.56 Nato 10.5in Upper Receiver What firearm models does the manufacturer say Faxon Firearms Duty Series AR-15 5.56 Nato 10.5in Upper Receiver is compatible with? The manufacturer suggests that Faxon Firearms Duty Series AR-15 5.56 Nato 10.5in Upper Receiver is compatible with AR-15Faxon Firearms FX-URG-D556105SA9-C-SR: Duty Series AR-15 5.56 Nato 10.5in Upper Receiver Socom Carbine Length 1-8 Twist 1/2x28 w/BCG Supressor Black