I have shot hundreds of rounds through my M4 with the Briley handguard attached. Everything from bird shot to 3" magnum rounds and not once has it become loose in any way. Not sure why yours did, maybe you did not seat it correctly. I know that I have seen some guys have that issue, thinking they had it seated all the way down and they didnt. Maybe call Briley and they can walk you through the process, also, having the Benelli M4 LE version, you need to put a washer where the Briley hand guard sits. There can be many different reasons as to why your handguard got loose but the B & T one is pretty cool. I was actually wanting to get that one before I found the Briley handguard, the only problem was trying to get one was almost impossible at the time.