[MR1 30 Round Mags]

I read that there were issues with Pmags.

[MR1 30 Round Mags]

I've read that the MR1 is a little picky when it comes to certain 30 round mags. Does anyone have some recommendations?

[MR1 Problem?]

Thanks for the reply.

[MR1 Problem?]

I just recently purchased the MR1 and test fired it today using Federal 223 55 grain rounds. After about 70 rounds I noticed shell casing marks on the upper receiver at the rear of the bolt. Is this normal?