It is very important to clean your bolt and bolt carrier group. I think I take more care on that than I do the barrel, as I usually I just run a bore snake through it and call it good. I use a copper solvent every 3rd or 4th range day, but have experienced little copper build-up.

Because it is a gas impingement rifle, where gas and unburnt powder is directed back into the action, the opportunity for carbon build-up to occur is pretty high. Just take a look at the tail of your bolt after firing a few hundred rounds. The firing pin goes through the tail. Imagine enough carbon building up to make your firing pin sticky. Slim chance, but a possibility.