breaking in a new BCG

[belizejet]

Any tips on breaking in a new BCG? I lubed it up and dropped it into my M&P 15. It turned it into a single shot rifle. Dropped the old one back in and the rifle ran like a sewing machine. Not happy but I might be doing something wrong.

[ray1970]

There must be something wrong with the new assembly. Hard to say what it might be.

[belizejet]

It was cheap. It was $99 from Midway USA. It had mixed reviews. I guess I should have avoided it and spend an extra $30-50.

[ray1970]

I've just got to ask... why would you buy a $99 bolt carrier assembly to replace the one in your M&P rifle? Seems like kind of a downgrade rather than an upgrade? Just curious.

[belizejet]

Its a new build for a 300BLK. I dont have a barrel so I just dropped it in my 5.56 rifle to break it in.

[belizejet]

The only difference between the two carriers is that the new one has more metal on the bottom making it a bit heavier. I hear there are 3 or 4 different carriers out on the market. This one said it was M-16 bolt carrier group mil spec and same material as all the other BCG's. Too good to be true I guess.

[ray1970]

I'm sure whatever is wrong with it is probably a quick, easy fix. You'll have fun with the 300. It's a neat little round to play with.

[cofi]

Check to make sure the extractor has the correct spring plus the little rubber post and o ring other then that lube the crap outta it

[BPTactical]

Check for staggered gas rings and gas ring tension. Check the gas key screws for tightness and properly staked.
Wash the carrier without the bolt in lacquer thinner or similar, make sure it is impeccably clean. Place ONE drop of bore cleaner or penetrant such as Kroil down the gas key. Give it a few minutes and check for any evidence of the solvent weeping between the key and bolt carrier. There should be none. If there is any the gas key needs to be fitted, lapped and fastened CORRECTLY.

You can tell very easily if the carrier is M16 cut or not. On a 16 carrier the the mill cut on the bottom "tail" of the carrier continues all the way to the end of the carrier.

[MarkCO]

^Yup.