How often should the carbon be cleaned off of a BCM bolt assembly? Is it possible to have a malfunction if if there was too much carbon on the bolt assembly?

A malfunction is always a possibility, but not often from too much carbon buildup, unless you're maybe shooting black powder loads or something crazy like that.

I've personally run a rifle/bolt over 10,000 rounds in full auto without cleaning as an endurance test, and not had a carbon-based stoppage (most stoppages are magazine related). I do not recommend that, but it can be done.

Keep it wet and keep it clean. No issues. If you can't clean it keep it wet.

You can basically clean it as much or as little as you like. Some guys take pride in a dirty rifle. Me personally I clean after every range trip, whether it was 60 or 600.

To be honest I enjoy cleaning ARs.

Before it becomes a problem.


Well, it is not possible to have a malfunction if the bolt is clean....(assuming the things works in the first place.)

There are several reason why you should periodically clean firearms...

1) They make less of a mess in your house if they are not dripping oily gunk all over the place.
2) They may work just fine dirty, but you know 100% that they work clean.
3) MOST IMPORTANT - It gives you a chance to inspect all the parts for wear, damage, and other evidence of impending failure.  This is why I have a pile of brand new unused spare replacement part, I don't just replace things because they have a few thousands rounds on them.  And generally speaking things don't develop cracks or wear in a hundred rounds or so.  Unless you shoot an awful lot per session, you should see problems before they become failures.

^^^^^ Item #3 is true for any firearm. Just cleaning it is only 1/2 of the equation. You should inspect parts and replace worn or broken parts.

I try to do it every range trip no matter the rounds fired. In some cases I got to the range more than once before cleaning. Like this week.

I went Monday for a quick session with a co-worker before we went to a meeting and I am going again later today but I did not have time all week to do a clean.

Before I go I will quickly bore snake the gun and wipe down the BCG and look for issues. Thorough cleaning will not happen until Sunday.

Sounds good. I usually clean everything after a range trip. The carbon that builds up on the bolt assembly is a pain in the azz to get off even with carbon killer.