Mercury Precision AR 9mm Complete Bolt Carrier Group

An AR-15 9mm bolt carrier group is the critical piece of a pistol caliber upper receiver that houses many important parts such as the firing pin, pistol gas key, cam pin, extractor, and bolt. With all these pieces working together the BCG can grab and feed another round out of a detachable magazine, chambers, and is ready to fire and extract a spent cartridge. During the extraction of a cartridge, the BCG works to absorb the force of the explosion by expanding gas in the carrier. During this process, the gas pushes the spent cartridge rearward with enough inertial force to send the Bolt Carrier Group back into the buffer tube which helps to minimize the recoil of your gun when firing and the cycle will repeat for subsequent shots. For 9mm bolt carriers, the bolt head is flat and is critical in creating a seal on the blow-back design of AR-15 9mm Pistol Caliber Carbines.

About this BCG: This BCG is an AR-15 compatible design, allowing use with 9mm Luger (9x19) cartridges. The 9mm AR-15 bolt carrier is also machined from 8620 Alloy Steel and is completed with a Nitride finish. This BCG comes with the ability to be full-auto compatible. MPI testing has also been done to ensure that there are no structural flaws to this BCG.

Caliber Compatibility: 9mm Luger (9x19) - This BCG is designed for the 9mm caliber. The most common pistol cartridge in the United States.

Finish: Nitride - Nitriding is a process during manufacturing that diffuses nitrogen into the steel to make a case-hardened surface for improved resistance and strength. A Nitrided BCG typically has a gloss black texture. Nitrided Bolt Carriers have increased resistance from heat, and corrosion.

Material: 8620 Alloy Steel - Body - 8620 Steel is a carburized alloy steel meaning carbon was added to increase hardness of the steel. 8620 is known for its high case toughness and high core toughness. Made mostly of nickel concentrate, this steel can easily withstand the firing stress of the BCG under operation.

Gas System: Direct Blow Back - Pistol Caliber Carbine AR-15 rifles do not tap off gas from the barrel and work in a direct blowback configuration, therefore the gas key is installed to index alongside the charging handle to allow manual operation of the platform.