Mil spec M16 Bolt Carrier Group - Geissele contracted premium BCG

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Mil spec M16 Bolt Carrier Group - Geissele contracted premium BCG

ultra premium phosphated BCG for M16, AR15 and M4 rifles and AR pistols

This is the BCG that Geissele installs in their URGi upper receiver groups.  Contracted by Geissele from a major defense manufacturer, this is one the better bolt carrier groups on the market  The manufacturer of this BCG makes many of the BCGs for other name brand military weapons.  The BCG comes in protected wax coating and shrink wrapped protective plastic wrapper, or in a Geissele branded plastic tube

The mil-spec BCG is what Charlie's calls our "premium line."  There are many different grades of bolt carrier groups, and most will get the average job done just fine.  But if your life depends upon the parts in your weapon, this BCG is among the best.  We can name names of other brands that we also prefer.  Some of those names are made by this defense contractor.  Geissele trusts it in their uppers, so you can too.

The components of this bolt carrier group has been stress treated and is designed for durability. The carrier is machined from AISI 8620 aircraft quality steel with an M16 full auto profile with a phosphate coating. The bolt is made from Carpenter 158 steel alloy and has been magnetic particle inspected and high pressure tested, which is what you would expect from an ultra premium mil spec BCG.  Every part has been made to the highest standard and inspected to prevent premature failure. The gas key is 4130 Chrome-Moly steel and has grade eight properly staked hex screws.

Note:  This is not manufactured by Geissele, but was contracted by Geissele for use in Geissele manufactured upper receiver groups and rifles before Geissele launched thier own brand of "nanoweapon" gun parts.  We are not permitted to mention the manufacturer, but it is one of the larger defense contract manufacturers.


  • 8620 steel constructed carrier
  • HPT / MPI
  • Magnesium phosphate finish
  • Full auto M16 profile
  • chromed bore and gas key
  • Carpenter 158 alloy bolt (shot peened)
  • 4340 Tool steel extractor (shot peened)
  • S7 Tool steel ejector (shot peened)
  • 4130 chrome-moly steel gas key with staked hex screws
  • 4340 chrom3-moly cam pin
  • 8640 steel alloy firing pin with chrome plating