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Brownells
A Brownells AR-15/M16 5.56mm bolt carrier group with nickel-boron coating is the heart of a reliable semi-auto rifle build. This complete BCG is engineered for shooters who demand durability without overpaying—whether you're assembling an entry-level duty rifle, a competition platform, or refreshing an existing upper. The nickel-boron finish resists corrosion and reduces friction, keeping your action running smooth through thousands of rounds.
Brownells built this carrier from 8620 steel with a hardened finish, paired with a 9310 steel bolt that's heat-treated and shot-peened for impact resistance. Every unit is magnetic particle inspected (MPI) to catch internal flaws before it ships to you. The extractor comes with a rubber insert and spring for reliable case extraction, while the gas key is torqued and staked to mil-spec standard—details that separate a precision part from a budget compromise.
The assembly is complete: bolt, bolt carrier, gas key, firing pin, cam pin, and retaining pin all ready to drop into your upper receiver. Designed for 5.56 NATO ammunition across all common variants, this BCG performs equally well suppressed or unsuppressed, with standard or enhanced buffer systems. It's the kind of component that lets you focus on shooting, not worrying about reliability.
| Product Type | Complete Bolt Carrier Group |
| Caliber | 5.56 NATO |
| Compatibility | AR-15 / M16 |
| Bolt Material | 9310 Steel |
| Bolt Finish | Heat-treated, Shot-peened |
| Carrier Material | 8620 Steel |
| Carrier Finish | Hardened |
| Coating | Nickel-boron |
| Quality Control | Magnetic Particle Inspected (MPI) |
| Includes | Bolt, Carrier, Gas Key, Firing Pin, Cam Pin, Firing Pin Retaining Pin |
Yes. This BCG is designed for both AR-15 and M16 platform uppers and is fully compatible with all standard 5.56 NATO chambers.
Nickel-boron coating offers superior corrosion resistance and lower friction than traditional parkerized finishes, which can improve reliability and make cleaning easier—especially valuable if you run your rifle wet or in harsh conditions.
This is a true complete BCG: bolt, bolt carrier, gas key (pre-torqued and staked), firing pin, cam pin, and firing pin retaining pin. It's ready to install in any compatible upper receiver.
MPI detects internal defects in the steel that would be invisible to the naked eye but could cause catastrophic failure during use. It's a quality assurance step that separates precision components from budget parts.
Brownells
A Brownells AR-15/M16 5.56mm bolt carrier group with nickel-boron coating is the heart of a reliable semi-auto rifle build. This complete BCG is engineered for shooters who demand durability without overpaying—whether you're assembling an entry-level duty rifle, a competition platform, or refreshing an existing upper. The nickel-boron finish resists corrosion and reduces friction, keeping your action running smooth through thousands of rounds.
Brownells built this carrier from 8620 steel with a hardened finish, paired with a 9310 steel bolt that's heat-treated and shot-peened for impact resistance. Every unit is magnetic particle inspected (MPI) to catch internal flaws before it ships to you. The extractor comes with a rubber insert and spring for reliable case extraction, while the gas key is torqued and staked to mil-spec standard—details that separate a precision part from a budget compromise.
The assembly is complete: bolt, bolt carrier, gas key, firing pin, cam pin, and retaining pin all ready to drop into your upper receiver. Designed for 5.56 NATO ammunition across all common variants, this BCG performs equally well suppressed or unsuppressed, with standard or enhanced buffer systems. It's the kind of component that lets you focus on shooting, not worrying about reliability.
| Product Type | Complete Bolt Carrier Group |
| Caliber | 5.56 NATO |
| Compatibility | AR-15 / M16 |
| Bolt Material | 9310 Steel |
| Bolt Finish | Heat-treated, Shot-peened |
| Carrier Material | 8620 Steel |
| Carrier Finish | Hardened |
| Coating | Nickel-boron |
| Quality Control | Magnetic Particle Inspected (MPI) |
| Includes | Bolt, Carrier, Gas Key, Firing Pin, Cam Pin, Firing Pin Retaining Pin |
Yes. This BCG is designed for both AR-15 and M16 platform uppers and is fully compatible with all standard 5.56 NATO chambers.
Nickel-boron coating offers superior corrosion resistance and lower friction than traditional parkerized finishes, which can improve reliability and make cleaning easier—especially valuable if you run your rifle wet or in harsh conditions.
This is a true complete BCG: bolt, bolt carrier, gas key (pre-torqued and staked), firing pin, cam pin, and firing pin retaining pin. It's ready to install in any compatible upper receiver.
MPI detects internal defects in the steel that would be invisible to the naked eye but could cause catastrophic failure during use. It's a quality assurance step that separates precision components from budget parts.
