Yankee Hill Machine Company Black Diamond Specter XL Upper Receiver Features The Yankee Hill Machine Black Diamond Specter XL Complete Upper pairs a complete bolt carrier group and charging handle with a finished barrel assembly so the only step left is dropping it onto a compatible lower receiver. Chambered in .300 AAC Blackout this upper gives shooters a quick caliber swap option on the same lower useful for hunting home defense or suppressed range work. Yankee Hill Machine has long been known for in-house barrel manufacturing and that expertise carries directly into the fit and finish of this assembly. Builders who want a dependable factory-matched upper without piecing together individual components get a straightforward path to a running rifle. A non-threaded barrel keeps the muzzle profile clean for shooters who plan to run the upper as-is or add their own muzzle device down the line. The complete upper arrives ready to mate with any mil-spec AR-15 lower so there is no fitting or headspacing required by the end user. This kind of drop-in compatibility is what makes complete uppers a popular way to add a second caliber or configuration to an existing rifle platform. The Yankee Hill Machine Black Diamond Specter XL Complete Upper is available for sale at GrabAGun for AR-15 owners looking to expand into .300 AAC Blackout with minimal hassle. Yankee Hill Machine Company Black Diamond Specter XL Upper Receiver Specifications Manufacturer: Yankee Hill Machine Model: Black Diamond Specter XL Upper Receiver Caliber: .300 AAC Blackout Barrel Length: 16 Threaded Barrel: Yes Available At: GrabAGun