I have a new bushmaster bolt carrier. Thinking of replacing bolt with a new BCM bolt. Do I need to replace the carrier to?
You don’t really have to, but can if you want. Carrier doesn’t really wear. You do need to make sure the Gas Key is Properly Staked. Bushy screws in the Gas Key will back out eventually.
I would stake the gas key and upgrade the extractor insert and spring and just shoot it.
I would suggest buying a spare bolt though.
If the barrel is working for you, just leave it.
C4
Replace the extractor spring as mentioned.
Properly stake the gas key screws.
I’d run the current setup as is until it breaks.