Okay, so the mags are seating just fine, and I've taken a couple pictures of rounds that jammed. Maybe the markings will give someone some ideas.
These are the most obvious marks
And these are directly opposite the first set of marks
I'm also having the same problem with my sig p226, which also has 10rd mags, but I believe they are factory 10rders as opposed to the modified mags for my AR. The only thing they have in common is me, and I keep my guns spotless, so I don't think it's user error.
Anyone have any ideas? I'm a very unhappy camper when the gun I built lovingly with my own two hands fails on me