Question about replacing BCG's

[C4IGrant]

I wanted to post this for a range buddy of mine. If you wanted to replace a LMT BCG with a BCM should you simply replace the carrier, or get the whole thing from BCM? The rest of the parts are LMT, and the only thing in question is a MIM gas key with some metal chipped off the face. My thoughts were that the entire piece needs to be replaced, but he feels otherwise.

Also, when replacing a bolt after the gun has 1000+ rounds through it; does the new bolt need to be fitted, or the chamber head spaced? Or can you just drop a new milspec bolt in? The question comes from seeing those that carry a spare bolt, my guess is that it drops right in, unless the barrel is about shot out.

Thanks in advanced for the help.

Why not just order a gas key and replace that??


C4

[chadbag]

Iraqgunz, what is a field gage? I have swapped out several BCG and never checked this. ALL where either quality LMT, COLT or Denny's, but never had a problem?

headspace gauges come in 3 different sorts

GO

NO-GO

FIELD

field is a field expedient NO-GO meaning it may close on a NO-GO but still be OK as long as it does not close on the FIELD. At least as an expedient measure.

Ignoring the lack of true 5.56 gauges etc.

[Apollo11]

Why not just order a gas key and replace that??


C4

Done, thanks for the advice in this thread.

[Pappabear]

Field Gauge / Headspace Gauge

Instructions for use

Hey Surf, thanks. How often does this become or is a problem? Is it as a result of excessive use or improper specs on BCG or chamber? Or both / either?

[Iraqgunz]

I check headspace when I initially build my AR's and then once a year. If I know that I have been putting alot of rounds down range then I will check it more frequently. I would check the headspace anytime you start swapping BCG's around. I would also avoid swapping them around unnecessarily.

Oon the job all weapons are inspected at least once per year as per the TM and more frequent depending on usage.

Hey Surf, thanks. How often does this become or is a problem? Is it as a result of excessive use or improper specs on BCG or chamber? Or both / either?