Yeah, that is normal looking. Both my M6 and M6A3 look like that and have no issues (the A3 has several thousand rounds on it). Don't quote me, but *Edit: I think they make the BCGs in house* and Failzero does the NiB.
My bad, I have no idea why I wrote bolt. But thanks for the replies. I know it wasnt going to affect function but it looks like hell on a rifle like this IMO.