I am trying to sort out a feed jam on the JR Carbine. I had 2 of these failures in 300 rounds this weekend.
As far as I can tell the bolt is not sliding back all the way to be able to pick up the back lip of the cartridge. In the large version of the image you can see where the bolt started trying to pick up the round.
It does it with force. enough to damage the bullet and the casing.It will happen with or without the suppressor and all the mags are Glock factory mags.
Another thing that may or may not be related is that it is rattling all the nut loose. Had to pause a couple times to tighten up everything.