Originally Posted by WoodenPlank
I've seen various reports on what runs best in the LMT SBR uppers. I run an H2 in mine since I shoot mostly 5.56.
In this case, though, the bad key meant the buffer didn't make a difference. I tried it with a C buffer, and no joy.
Call LMT. They will tell you exactly what I said.
You may get away with it in some rifles or may not. But my guess would be you are running it on the edge of reliability and when things get dirty or close to being out of spec it adds up.
Maybe not. I could be wrong. Been wrong before.
Honestly, Your BCG should still run with one screw tight as the key should still be tight against the carrier. But again, maybe not.