K1L0

That's interesting, thanks for checking! I think it might be a BCG and rail tolerance thing, the marks at the back of the ejection port at least on my gun seem to be from the edge of the BCG striking the opening. The marks are on the edge closest to the BCG and it doesn't seem like brass could strike there since the bolt head is in the way when the BCG is pulled all the way back. I'll take a picture. Regarding JP standing behind products... My upper and lower receivers rattled against each other out of the box and JP has been ignoring my emails. I called and they said they would ship an oversized takedown pin but that was almost a month ago and I haven't received anything yet. In the meantime, I've just been using layers of built up super glue to take out the slop haha... Video of the rattle: https://youtu.be/rYovytIPOiQ

Is anyone else seeing some wear at the rear of the ejection port? It looks like casings have been hitting there, and there are also two marks at the top of the ejection port.

Oof ok, I'll reach out to them thanks. I did notice the pivot pin is the standard OD of 0.248" while the rear takedown pin was their oversize pin with an OD of 0.249". The standard pin has one big divot on the face, while their oversize pin has a big divot with a smaller one clockwise from the larger one. Do you happen to know which pin sizes are on your rifle?

I just received my black anodized JP-5 and noticed a decent amount of play between the upper and lower receivers at the pivot pin side. I can hear the rattle when turning the rifle over or pushing and pulling the upper and lower against each other. Anyone else notice this with their JP5?