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Chrome Lined Bolt Carrier Group - C158

Alpine Research

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The Alpine Research BCG is constructed from the finest components available. Every BCG is fully measured, gauged, and inspected before being assembled in-house by Alpine Research. We do not rely on any outside vendor's quality control processes, instead, we do 100% QC on all subcomponents and even fire test 100% of our carriers prior to placing them in inventory on the site.


Bolt: Carpenter 158 steel HP/MPI

Carrier: 8620 Tool Steel

Coatings: Mag Phos, chrome lined (gas key chrome lined)

Gas Key Fastners: Michiguns OCKS + staking, key to carrier is sealed

Ring: Sprinco

Extractor Spring: Sprinco 5 turn + insert

Ejector Spring: Sprinco



Q: Why don't you offer Nitride or NiB or any other coatings?

A: Right now we're sticking with Manganese Phosphate exteriors and chrome lined interiors for a few reason.  Primarily, mag-phos does a better job keeping the lube where you put it, instead of having it slick off during operation.  In my opinion, this is an extremely important factor when selecting a carrier, and the ease of cleanup is not.  Chrome lining is also desirable as it is an extremely hard wearing surface, ideal for inside the carrier where the bolt is reciprocating and rotating with each shot.

Q: Why Carpenter 158 and not 9310

A: Despite being on paper a stronger material choice after heat treatment, most of the bolt failures I'm seeing are 9310 bolts.  I like our C158 bolts because they are tough and hold up very well.  Will it last you forever?  Depends on how many rounds you shoot between now and forever.  If you're a high volume shooter you will eventually wear the bolt out and replacement will become necessary.

Q: Do you have replacement parts for components within the carrier?

A: Yes, however, not all will be listed on the site.  If you need something you don't see just shoot us an email and we'll get you taken care of.

Q: Can you headspace my bolt to my barrel?

A: If you buy an Alpine Research barrel on the same order this is done automatically.  If you have another manufacturer's barrel, you may ship it to us and for a nominal charge will will verify headspace for you.

All Alpine Research BCG's are guaranteed to be free from manufacturer's defects. Should you suspect your BCG has an issue or defect please contact us immediately. Warranty does not cover normal wear from use, wear or breakage from misuse or neglect.