Is it dangerous to share a bolt and BCG between uppers

[kd7nqb]

Here's my dilemma I have bushmaster AR and love it. Now I want to get a .300blk upper for it.

From my understanding I can use the same mags and same bolt and BCG for the .300blk. But some people seem very adamant that you should get a new BCG for each upper so the two wear evenly together.

My question is how big of a deal is it really and are there any safety issues or is it only a wear issue if I shoot tens of thousands of rounds.

My plan is basically to only use the .300 during hunting season.

 

[mizer67]

Your headspace could be a little on the loose side of "go", but you should be fine for the usage you describe.

Worst case you'll probably rob yourself of some accuracy.

You may want to get a no go guage just to be on the safe side.

 

[taliv]

the carrier doesn't matter, only the bolt. bolts are wear parts. you should replace them with new ones every 5-10k rounds anyway.

i the barrel/bolt was a matched set like you get from WOA or something i wouldn't swap it. but if it's a run of the mill part, sure, why not?

i personally also wouldn't do it long term since i lube my blackout and 556 differently. but if it's just a temporary thing until you find a BCG in stock somewhere, sure

 

[briansmithwins]

In theory it could cause increased wear of the barrel extension and bolt. In real terms, since AR bolts usually break between 10 and 20 thousand rounds, it probably won't make any noticeable difference.

The .mil manuals prohibit swapping bolts and say to check headspace when replacing a bolt, so the 'correct' answer is not.

BSW

 

[madcratebuilder]

Quotes from the 23&P Army manual.

Do not interchange bolt assemblies from one rifle to another. Doing so may result in injury. Doing so may result in injury to, or death of personnel.

The above is printed in several locations.

NOTE
Replacement of the bolt assembly will require that the headspace be tested

If excessive headspace, first replace bolt assembly and then recheck If headspace is not corrected, replace barrel assembly; then recheck with the original bolt to determine if the bolt is still good or If the bolt should be replaced also

The manual goes on to state you can use a used bolt in a new barrel (BE) a used BE with a new bolt, but DO NOT use a used bolt with a used BE.