Stern Defense Complete Upper Features The Stern Defense Complete Upper is built around a 6 inch .45 ACP barrel finished in Black Melonite and cut with a 1:16 twist to stabilize the heavier .45 ACP bullet. The mil-spec flat top receiver carries a laser engraved dust cover and forward assist machined from 7075-T6 aircraft grade aluminum and hard coat anodized for durability. Because .45 ACP cases run larger than standard 5.56 rounds the ejection port has been enlarged specifically to handle them without feeding or ejection issues. A mil-spec dry film lube in the bore and a mil-spec charging handle round out an upper built to function reliably from the first round fired. The dedicated bolt is machined from 8620 AISI steel with a mag-phosphate finish and arrives fully assembled with the firing pin spring retaining pin extractor and extractor spring already installed. It is compatible with both Mil-Spec and Glock pattern upper receivers and cycles Colt SMG and Glock magazines giving builders flexibility in magazine choice. The free float M-LOK handguard uses a secure clamp on mounting system that keeps it locked in place even under sustained fire or while shooting off a bipod and its 6061 aircraft grade aluminum construction is hard coat anodized for long service life. Finished entirely in Black with quick disconnect swivel holes built in this upper gives builders a complete purpose made foundation for a dedicated .45 ACP AR build. Stern Defense Complete Upper Specifications Manufacturer: Stern Defense Model: Complete Upper Caliber: .45 ACP Color: Black Mount Type: M-LOK Barrel Material: Chrome Moly Steel Barrel Finish: Black Melonite Twist Rate: 1:16 Barrel Length: 6 Handguard Length: 8 Receiver Material: Aluminum Receiver Finish: Anodized Handguard Finish: Black Anodized Thread Pattern: .578x28 Available At: GrabAGun