The Microbest BCG has been designed from the ground up with the most avid shooters in mind, using only the best materials available on the market today.  The bolt assembly is machined from Carpenter No. 158® steel, shot-peened, MP marked, HP tested, and has a tool steel extractor that is machined from bar stock. Microbest is the OEM manufacturer and supplier of bolt carrier groups for a lot of popular rifle manufacturers, including but not limited to, Bravo Company Mfg and Sons of Liberty. Microbest is trusted to build a bolt carrier group that exceeds the MIL requirements from the right materials and processes with great attention to detail.

Bolt Assembly:

• Bolt precision machined from Carpenter 158 alloy and vibratory tumbled
• Heat-treated and shot-peened
• Individual high pressure/proof (HP) and individually magnetic particle inspection
• Ejector from S7 tool steel, heat-treated and shot-peened
• 4 Coil Sprinco Extractor Spring
• Sprinco Ejector Spring
• Gas Rings 3 Mil-Spec
• Black Nitride Coated

Carrier:

• Machined from AISI 8620 steel
• Full-auto M16 profile
• Heat treated and Carburized/strain relieved
• Precision ground gas key interface
• Gas key from 4140 steel Heat Treated
• Grade 8 Gas Key Screws Staked, Phosphate Coated
• Black Nitride Coated

Misc:

• Cam pin from 4140 chromoly steel, heat-treated, Black Nitride Coated
• Firing pin from 8640 steel alloy, heat-treated, Black Nitride Coated
• Firing pin retaining pin from 1038 carbon steel, heat-treated, Black Nitride Coated