I won an auction for an LWRC DI 5.56 upper that I didn't expect to win and didn't really want to. (Got a decent deal though.) I was hoping to throw it on to a Stag lower I had lying around, toss on the VCOG, and sell it to a coworker. Well, it arrived today and that plan fell through. Works fine on a LWRC M6IC lower. Every other upper I have works on the Stag lower. But the LWRC upper doesn't work on the Stag lower. Fits a bit like it has an accu-wedge installed and the bolt will retract (with difficulty) about 1/2 inch before it stops. Think I'll be keeping the upper and convert it to .300 Blackout or maybe a Valkyrie. I'm gonna shoot an email to LWRC and see if I can get barrel for it. I don't really need another 5.56.