Quick fix for Better-Mag/CMMG 22lr upper interference

Wife and I are new to ARs and now have his/hers with BCM lowers. I wanted a realistic training rifle so went with the dedicated CMMG 22lr upper and Better-mag adapter.

The bolt would not lock bag although installation was proper. I won't go into the gory details, but I spent a lot of time looking for interference in the vicinity of the Better-Mag bolt lock adapter. Did a bit of filing and polisshing to no avail.

Short version: The Better-Mag is machined as a perfect fit into the mag well and extends above the mag well into the upper. The forward corners of the CMMG upper where it mates to the mag well have a larger radius than the Better-Mag and were slightly distorting the Better-Mag assembly thereby locking up the small adapter. 5 minutes of Dremel work on the two forward edges of the Better-Mag to increase the radius and the lock back feature works flawlessly. I let Redi-Mag know what I found so that anyone calling with this problem will get the correct information. Prior to this modification I had not problem mating my BCM upper with Better-Mag in place which should have been a clue.

I've only run Remington golden bullets and Federal Auto Match so far without incident.