The Adams Arms AA-15 in 6.8 SPC uses Adams' proprietary micro-sized piston operating system designed to retrofit the standard AR-15 upper without modifying the lower receiver. The piston system provides carbon-free operation in a standard AR-15 form factor. Type: Rifle Action: Semi-Automatic Caliber: 6.8 SPC Capacity: 26 Year introduced: 2013, USA Weight: 72 oz Overall length: 32.5" Status: Active Intended use: Hunting, Home Defense, Law Enforcement