Alright…here is the solution:
First, lube it up. Ar’s are meant to be wet.
Second, welcome to the world of 10rd pmag issues. The solution is 10 min and sandpaper. For some reason, when magpul designed the 10 they put a bump on the back of the mag. This bump interferes with a variety of ar10 lowers. They dont do it on the 15, 20, or 25 rd. So you need to sand the bump off.
Sand here:
Until it looks like this:
The bump makes the mag seat at an angle, with the back down and you get the bolt jumping over the rounds instead of stripping them.