Geissele Reliability Enhanced Bolt Carrier Group (BCG) for AR15 / M4 / M16

MSRP: $385.00
(You save $16.00 )
extremely limited supply, when in-stock, we sell out fast.

Geissele Reliability Enhanced Bolt Carrier Group (BCG) for AR15 / M4 / M16

Did Bill Geissele build a better mouse trap with the REBCG.  We think so.  There are other great bolt carrier groups, so why build another?  Not sure.  Probably because he could.  Maybe because Geissele is building everything else that makes a full rifle, so why not an enhanced BCG? 

I gotta admit, Charlie was skeptical.  But this one looks impressive.  I am not sure we will win Charlie over from his go-to bolt carrier and bolt, but this one comes pretty close.

Geissele spared no effort in design, craftsmanship, machining and materials.  The first thing that sticks out is that the extractor is a lighter colored steel, and stands out from the rest of the Bolt.  The next thing you notice is this is not a standard phosphated steel, but a slick coating.  You might be tempted to think Nitriding, or QPQ, or DLC, or Ion bonding.  These are all great coatings, but Geissele developed their own coating that is applied in a very different fashion,  No hot acid baths.  No vacuum chambers with positive and negative ions floating in space.  The coating is in the family of durable solid liquids.  Geissele calls it Nanoweapon coating, and the Nanoweapon coating has been a few years in the making and testing.  Sounds a lot like DLC with some marking buzz, but our assessment is that it is a solid offering.


  • Full auto rated
  • M16 Profile
  • 8620 Carrier
  • C158 Bolt
  • H13 steel cam pin
  • Improved upper rails
  • Nanoweapon Chrome Nitride finish
  • HPT and MPI

The Reliability Enhanced Bolt Carrier Group (REBCG) is a 5.56mm full-mass, full-auto rated M16/M4 bolt carrier group.  The carrier is machined from mil-spec 8620 steel, and features a properly torqued and staked, chrome lined, gas key. The cam pin is machined from an advanced medical steel typically used to produce medical instrumentation known as H13, it is then coated with Nanoweapon (Chrome-Nitride) for maximum corrosion and wear resistance. The extended upper rails on the carrier also provide much greater stability and dramatically increase feeding reliability. The Carrier is coated with Nanoweapon for maximum corrosion and wear resistance.

The Geissele Stressproof Bolt is forged and made from Carpenter 158 steel allow.  Geissele engineers worked the Carpenter Steel metallurgists to produce a new allow known as Carpenter 158+. This material is cleaner with less impurities, ultimately making it stronger and more consistent. Geissele believes the combination of forging and Carpenter 158+ allow steel makes the bolt capable of 5 times the life of a mil-spec bolt. Each bolt is then rigorously inspected, high pressure tested, mag particle inspected and coated with Nanoweapon for maximum corrosion and wear resistance.

Nanoweapon is a family of coatings similar to DSL (Durable Solid Lubricant) that was developed by Picatinny Arsenal (US ARMY ARDEC), and is available exclusively on Geissele parts. Geissele spent 3 years with the research and development company that worked with Picatinny to develop the coating to tune it into what it is today, which Geissele believes is one of the best coatings for firearm components.  The coating is applied at low temperatures so it does not affect the metallurgy of the part, and has a surface hardness equivalent of 82HRC. At that hardness, it is harder than sand, easily rejecting carbon and making cleaning a breeze, on top of allowing the firearm to operate normally with less lubrication.