A few months ago I acquired a Colt 6530 that was unfired.  Since then I've probably put something like 1,500 rounds through it, and on the last few cleanings I've noticed that the bolt has become pitted.

The pitting occurs on the side of the gas rings away fromm the bolt face.  It's not terrible, and at first I thought it was just carbon buildup - but it doesn't seem to scrape off.

Of the 1,500 rounds I've fired, probably 300 were Lake City Lot 7 and 1,200 were South African battlepacks.

Anyone else have this?  Is it normal or is it something I should be concerned about?

If your talking about light pitting on the tail of the bolt where carbon usually builds up it is probably not going to be a problem.