New, never installed Chrome Microbest BCG. Will ship and purchasers expense if not local to East Cobb. (Shipping costs have been around 10-15 for a padded envelope.)
Details copy and pasted from a site.
Bolt Assembly:
Details copy and pasted from a site.
Microbest BCG Mil-Spec C158 HPT/MPI 5.56 Bolt Carrier Group – Chrome w Phosphate Extractor
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.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
- Hard chrome-plated finish w Phosphate Extractor
- 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
- Hard chrome-plated finish
- Cam pin from 4140 chromoly steel, heat-treated
- Firing pin from 8640 steel alloy, heat-treated, hard-chrome plated
- Firing pin retaining pin from 1038 carbon steel, heat-treated
