Brass is softer than steel, and the locking lugs, feed lips, or any other sharp objects can gouge into it more easily.Seems like the brass bullets are getting hung up on the feed ramp on the far side. Why wouldn't the steel hang also? No fte to speak of r
I would add to this that you might benefit from polishing the feedramp to remove any sharp areas or burrs present on the "fins".Brass is softer than steel, and the locking lugs, feed lips, or any other sharp objects can gouge into it more easily.
For proper feeding, the magazine must feed to the center. Many AR mags feed the double stack ammo a bit to the right and left. The PLR-16 doesn't like this. Hence, the recommendation in the stickied PLR-16 FAQ to try the factory mag and a Magpul PMAG.