My AR is a Bushmaster M4A3 in 7.62x39. It has around 350 rounds through it. It was clean and lubricated when I started.
I wanted to see if it would properly eject some ammo I purchased (it's picky). I did the following:
1. Set the weapon to SAFE.
2. Inserted the mag with the bolt locked back.
3. Released to bolt, letting it chamber the first round.
4. Pull back the charging handle, thus ejecting the unfired round
5. Released the changing handle, loading the next round.
I did this with three types of ammo. One known PASS, one known FAIL, and the test ammo. It failed, so I won't buy 1k rounds of that this afternoon.
BUT, as I looked at the rounds afterwards, I noticed that nearly all of them had what appeared to be a light strike in the center of the primer. And I mean <i>very</i> light... equal to or less in depth than the indented letters on the case bottom.
So I am asking the Experts... What is this? Should I be concerned?