SOLGW Hard Chrome Bolt Carrier Group (BCG) – 5.56 158 Carpenter SP/HPT/MPI


SOLGW Hard Chrome Bolt Carrier Group (BCG) – 5.56 158 Carpenter SP/HPT/MPI


SOLGW looks at the bolt carrier group as the heart of the gun. If the gas port is the lungs, then the bolt carrier group is the heart. It’s what drives the entire gun. If you look at the AR platform’s cycle of operations, everything happens around the bolt carrier group. Locking, unlocking, extracting, ejecting…all of it begins with the bolt carrier group.

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1 in stock


Built for the most demanding applications, the Sons of Liberty Gun Works 5.56 NATO Bolt Carrier Group (BCG) is meticulously crafted from premium materials and subjected to rigorous quality control measures. This BCG boasts a Carpenter Technology No. 158 chrome-nickel alloy bolt, 4340 tool steel extractor, and S7 tool steel ejector, ensuring exceptional strength and wear resistance.


  • Bolt: Carpenter Technology No. 158 chrome-nickel alloy
  • Extractor: 4340 tool steel (superior to 4140)
  • Ejector: S7 tool steel
  • Carrier: AISI 8620 aircraft-grade alloy
  • Gas Key: 4130 Chromoly steel with hard chrome interior
  • Magnetic particle inspected, high pressure tested, shot peened
  • Full auto test fired at assembly
  • Mil-spec and ASTM compliance
  • Heat treated for optimal strength


  • Precision machined from Carpenter Technology No. 158 chrome-nickel alloy
  • Heat treated per mil-spec,
  • Shot peened per ASTM B851/SAE AMS2430S,
  • Vibratory tumbled
  • Individual high pressure/proof (HP) test
  • Full Auto test fired at assembly
  • Individual magnetic particle inspection ASTM E1444/E1444M (MP)
  • Markings deep laser engraved (SP=Shot Peened, HP=High Pressure Tested, MP=Magnetic Particle Inspection.)


  • Precision machined from 4340 tool steel alloy per SAE AMS6415T/AMS6484D (vs 4140)
  • Heat treated
  • Shot peen per ASTM B851/SAE AMS2430S

Extractor Retaining Pin:

  • Precision machined and ground S7 Tool Steel
  • Heat treated per ASTM A681-08
  • Shot peened per mil-spec print

Extractor Spring:

  • Tactical Springs/Sprinco 5 coil, ASTM Grade A401 Chrome Silicon wire stock
  • Heat treated
  • Stress relieved, Molybdenum-Disulfide infused
  • Cryogenic processed (Hidden post winding)
  • Mil-spec black insert/synthetic elastomer extractor buffer (nitrile-butadiene, shore hardness 80+/-5 durometer per MIL-PRF-6855)


  • S7 Tool Steel
  • Heat treated per ASTM A681-08
  • Shot peened per Mil-Spec
  • Ejector Spring:
  • Heat treated
  • Mil Spec

Gas Rings:

  • Standard stainless steel per Mil-Spec X3


  • Machined from AISI 8620 aircraft quality alloy per ASTM A108/A322-13
  • Full auto profile
  • Heat-treated
  • Carburized/strain relieved, hard chrome bore
  • Precision ground gas key interface
  • Sons of Liberty Battle Flag logo deep laser engraved

Gas Key:

  • Machined from 4130 Chromoly steel alloy per ASTM A108/A322-13
  • Heat-treated; hard chrome internal
  • Permatex sealed
  • Grade 8 hex screws torqued and staked Hidden per mil-spec

Cam Pin:

  • Precision machined 4340 Chromoly steel alloy per SAE AMS6415T/AMS6484D
  • Heat-treated/processed per mil-spec
  • Solid film lubricant applied and cured per mil-spec

Firing Pin:

  • Precision machined 8640 steel alloy
  • Heat treated/processed per mil-spec
  • Hard chrome plate

Firing Pin Retaining Pin:

  • Precision machined from 1038 carbon steel
  • Heat-treated/processed per mil-spec

Find out why this is the Best Bolt Carrier Group in the industry. Son’s Of Liberty Gun Works


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