AO Precision C158 SP/HPT/MPI 5.56 Black Nitride Bolt Carrier Group

AO Precision C158 SP/HPT/MPI 5.56 Black Nitride Bolt Carrier Group

AO Precision has provided BCGs to large military contractors such as FN America and large commercial retailers who re-brand and sell these at a considerable mark-up. 

Bolt

• Machined from Carpenter Technology No. 158 alloy.
• Heat treated
• Shot peened per ASTM B851/SAE AMS2430S
• Individually High Pressure Tested (test fired)
• HP proof testing, 100% using a high pressure M197 or SAAMI commercial equivalent, without evidence of failure
• Individually Magnetic Particle Inspected after Initial Test Fire
• Black Nitride Finish

Extractor

• 4140 Steel per ASTM A108, cold drawn and stress relieved BHN 187-22
• Phosphate Finish
• Extractor Spring
• Black Extractor Insert
• Viton O-Ring

Carrier

• Machined from AISI 8620 aircraft quality alloy per ASTM A108/A322-13
• Full Mass M16 Profile
• Stress Relieved
• Black Nitride Finish

Gas Key

• Machined from 4130 chromoly steel alloy per ASTM A108/A322-13
• Grade 8 Hardware
• Properly Staked
• Hard Chrome Internal
• Permatex sealed