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

From: $89.99


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. Ask us about discounts on an order of 2 or more.

Buy the base complete BCG from AO, or upgrade it with our selection of parts for a little extra!


Machined from 9310 Steel
Heat treated
Shot peened per ASTM B851/SAE AMS2430S
Individually High Pressure Tested (test fired)
Individually Magnetic Particle Inspected after Initial Test Fire
Manganese Phosphate Finish


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


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


Choose an upgraded gas key and gas key screws, you can also choose a different firing pin and/or cam pin.

If you do not choose any additional parts, the BCG will be sent as is, if no assembly is selected the BCG will send as is, with the additional parts ordered.


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