Could this be (gulp) rust??

[Ilove2shoot]

load and shoot....load and shoot...load and shoot........clean it off, oiil it up and repeat many many many times.......then inspect.

[QuadBomb]

Is this what the bolt looked like before cleaning? Sometimes there is discoloration on a bolt from small particles of brass from the cartridges and I have also seen discoloration caused by the bristles of a metal brush (like a bore brush). You can usually just wipe this off with clp and q-tips.

I cleaned it off and put it away for a month or so before breaking it down again. That's what it looked like last weekend when I pulled it out.