marks on fired brass

[jet80tv]

I was wondering what causes these marks? I only recently started checking my brass for any peculiarities on the case and at the rim where contact is made. Some of my empties have these marks, some have none and some just have them faintly. Thanks in advance
9762

[shua713]

it is where the case hits the ejection port when being ejected.

[jet80tv]

well atleast its pretty consistent than, thanks

[hotrodder636]

it is where the case hits the ejection port when being ejected.

Either that, or could it be the deflector? Not correcting but rather asking.

[rocketman]

Am I wrong to think this weapon might be a bit over gassed? I'm asking because I don't know...not being a smart ass.

I have an upper that was built using an older pencil thin Bushmaster 1/7 barrel. I had it cut and pinned at 14.5" and mounted it on a carbine lower I had laying around. Last week I went out and shot it and it beat the shit out of the brass. The dings were as bad as what you have pictured maybe even a smidge worse. I came home thinking I was going to put an H or maybe even an H2 buffer in it and trade out the simi-auto carrier for a full-auto to smooth it out a bit.

Today I decided to stick an A1 stock and rifle buffer system on it and put a BCM BCG in it and go wear it out. I shot about 200 rounds thru it (same mil surp 5.56 ammo) and the brass doesn't have a mark on it. It's going to make a great trunk gun.

Anyway I'm pretty sure my little upper was way overgassed. I wonder if yours is?