Rosco Bolt Carrier Group Features The Rosco Manufacturing Bolt Carrier Group is Melonite finished a nitrocarburizing process that leaves the stainless steel surface exceptionally hard and corrosion resistant. That finish reduces friction inside the receiver which means smoother cycling and easier cleaning after a long day of shooting. Because the group is full auto rated it is built to handle sustained cyclic use well beyond what a semi automatic rifle demands in normal service. The bolt is matched to the barrel a step that helps ensure proper headspace and consistent lockup shot after shot. Proper staking of the gas key is a detail that separates a reliable bolt carrier group from one prone to failure and Rosco performs this step to keep the key secured under repeated recoil impulses. Compatible with both 5.56 and .300 AAC Blackout chamberings this bolt carrier group suits shooters running multiple uppers on a single lower receiver. At 0.78 lbs it matches the weight profile AR-15 owners expect from a mil spec style carrier group so reliable cycling and spring timing are preserved. Whether replacing a worn factory part or building a new upper from scratch the Rosco Manufacturing Bolt Carrier Group is available for sale at GrabAGun. Rosco Bolt Carrier Group Specifications Manufacturer: Rosco Model: Bolt Carrier Group Type: Bolt Carrier Group Material: Stainless Steel Finish: Black Melonite Firearm Type: Rifle Weight: 0.78 lbs Caliber: 5.56 Available At: GrabAGun