I ordered a complete 14.5” carbine gas length AR upper in 5.56 from a large manufacturer with a sterling reputation for reliability/build quality. I mated this upper to a lower from the same company. For a long while I could only shoot this rifle at a range that only allowed slow firing, i.e. greater than one second between trigger pulls. Shooting at this range, the rifle was 100% reliable. Recently I began shooting at a new range that allows rapid firing. Whilst firing rapidly, the rifle would have 1-2 malfunctions per 30 round magazine. Each malfunction ended with the expended brass becoming wedged between the bolt face and the distal, inside edge of the charging handle. I tried many things to fix the issue but without success. The other day, I decided to look at the bolt for issues but all seemed well until I noticed a small stamping that reads “6.8mm” (presumably 6.8SPC). I’m embarrassed that I never noted this before when cleaning the bolt or when I was trouble shooting it previously (sometimes you don’t see a problem that you’d never look for in the first place). I replaced the entire BCG with a new one from the same company and fired 100 rounds through it, encountering one failure to feed. So, in the short term, the issue seems to have been remediated.
I contacted the company and they have sent me an RMA. I’ll be sending the upper in tomorrow.
Obviously, this company should not have sent me a 5.56 upper with a 6.8 bolt in the BCG. Mistakes happen, and I’ve only posted the aforementioned history of the upper to properly set up my question to you.
Given this upper has 600 or so rounds through it with the 6.8mm bolt, should I expect damage has been done to the bore or any other components of the upper? I can’t see anything grossly wrong, but I don’t have a trained eye. I’m asking for your thoughts because I want to be able to have a informed discussion with this company once their armorers have the upper in hand. I want to ensure they have done more than a cursory investigation for damage if it seems there could be long term consequences that may not necessarily manifest at this time. Would any of you, for example, go ahead and change out the barrel just of the basis of the history I provided above? (I’m not fishing for a new barrel, upper or anything like that, this was just an example question I was spit balling).
Anyway, I thank you all for any thoughts you may provide.
Kyle
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Originally Posted by markm
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