Bolt carrier groups ?

[kbi]

I just relized something that had me again scratching my head. Ive owned a lot of AR's(13 over the past 14 yrs) and It just dawned on me .

Ive never taken the carrier group from one and put it in the other rifle .

And since Im planning putting something together in the near future are their any precautions I should take when buying a upper(LMT.CMMG,CMT,RRA,BC) with no bolt carrier?

Im figuring if I get a barreled upper from a manufacturer and they did their thing headspacing the barrel I should just be able to get a complete carrier group from again a reputable distributer/manufacturer (CMT,LMT)and drop it in right?

[C4IGrant]

I just relized something that had me again scratching my head. Ive owned a lot of AR's(13 over the past 14 yrs) and It just dawned on me .

Ive never taken the carrier group from one and put it in the other rifle .

And since Im planning putting something together in the near future are their any precautions I should take when buying a upper(LMT.CMMG,CMT,RRA,BC) with no bolt carrier?

Im figuring if I get a barreled upper from a manufacturer and they did their thing headspacing the barrel I should just be able to get a complete carrier group from again a reputable distributer/manufacturer (CMT,LMT)and drop it in right?


No worries if your buying all new items and they are all quality.


C4

[PalmerB]

In a perfect situation you should be fine, as C4IGrant stated.

A set of gauges may be used (Go, No Go, Field) to check the head spacing. On a new build I also check the first cartridges for signs of over pressure or other abnormalities.

It is your face on the cheek weld, and therefore your call on what level of precautions you feel you will need.

[Robb Jensen]

I'm a little anal about stuff, when I change a gas tube (on my own guns) I also change the carrier key, gas rings and use new screws on the gas key. Not needed 98% of the time, but like I said I'm anal.

If a gas key shoots loose I replace it instead of just cleaning it and re-torquing/staking.

[Voodoochild]

better to be safe then sorry.

[Navy87Guy]

I'm new to AR's, so bear with me....

I was reading the tech manual for our MK 18 rifles (the 10.5 in carbine -- cool stuff!). There are numerous warnings not to swap BCG's between rifles. From this discussion, though, it doesn't sound like a problem.

Is there some kind of "wear in" that happens with use that makes a BCG unsuitable for use in a different weapon? Not that I am going to have lots of AR's lying around to experiment with -- I'm just curious. The Navy tech manuals are pretty explicit about not doing it.

Thanks!

Jim

[-Wes-]

I've always been told that carrier swaps are cool but it's best to keep bolts with their barrel since they wear on eachother. The higher the round count the more I'd be wary of using the bolt in another upper, I would think SBR's would wear even faster due to the harshness of the cycling.
...and just jokingly, the Navy manuals also told us to never re-use fasteners on our F/A-18C fuselage panels, just for ONE example. I know why, because as with any screw, once it's torqued it's grip stretches. If we did follow the rules though, we would have needed a truck load of fasteners a day.
I'd definitley put new ones in a carrier key though.

[Robb Jensen]

I'm new to AR's, so bear with me....

I was reading the tech manual for our MK 18 rifles (the 10.5 in carbine -- cool stuff!). There are numerous warnings not to swap BCG's between rifles. From this discussion, though, it doesn't sound like a problem.

Is there some kind of "wear in" that happens with use that makes a BCG unsuitable for use in a different weapon? Not that I am going to have lots of AR's lying around to experiment with -- I'm just curious. The Navy tech manuals are pretty explicit about not doing it.

Thanks!

Jim

Jim,

When in the manuals you see BCG it means bolt carrier group, which means the bolt, bolt carrier, firing pin, cam pin and firing pin retaining pin all assembled. The bolt itself is headspaced to the barrel/barrel extension and shouldn't be swapped between different rifles without checking with a USGI Field gauge. If the carriers alone are switched between two different rifles it won't change the headspace in either rifle and most of the time everything will work fine.

I don't like to swap just carriers among different rifles (other than just testing for function, like a possible leaking carrier key). This is because I'm concerned how the carrier key will then fit the gas tube. Most of the time everything will work fine. When one (the gas key or the gas tube) needs replacing I like to replace the key and the gas tube as I believe they should wear in together. It's the same reason on a pistol when changing recoil springs I also change the mag springs (even if they had been working 100%), and extractor spring. I do it simply because one directly effects the other.