The One Horse M16 Bolt Carrier Group (part no. OH-UBC01) is built for 5.56/.223 and .300 Blackout AR15s, using a 9310 tool steel bolt and an 8620 steel carrier for durability under sustained use. One Horse runs the full mil-spec heat-treat and testing process on this carrier group, then finishes it in salt-bath nitride for corrosion resistance and easy cleaning.

Key Specifications

• Machined from 9310 tool steel for the bolt, a stronger alloy than mil-spec carpenter steel for high round counts.
• Carrier machined from 8620 steel, matching mil-spec carrier material.
• Undergoes full mil-spec heat treatment and magnetic particle inspection (MPI), catching subsurface flaws before the part ships.
• Finished in salt-bath nitride, which resists corrosion and cleans up faster than a standard phosphate finish.
• Uses an S7 tool steel extractor with a spring insert and O-ring for more consistent extraction.
• Ships with a staked gas key and Grade 8 fasteners, preventing the key from loosening under sustained cycling.
• Cut with forward assist serrations and chamfered lug faces for reliable engagement and feeding.

Frequently Asked Questions

Will this BCG work in both 5.56 and .300 Blackout uppers? Yes, both cartridges share the same bolt face and headspace, so one BCG covers either chambering.

Is the gas key staked at the factory? Yes, it ships with a staked gas key and Grade 8 fasteners so it won’t loosen under use.

What testing does this bolt go through? Full mil-spec heat treatment plus magnetic particle inspection (MPI) to catch subsurface flaws before it ships.

Buy the One Horse M16 Bolt Carrier Group

Order this nitride-finished BCG from One Horse. Ships fast from a Lubbock, TX gun shop. Browse our full AR bolt carrier groups selection for more builds.