u/montythenondog

I have solved two separate malfunctions that were both caused by the BMA. Both were fixed by removing some material with a small hand file.

Issue 1. Hammer follow - For those of you who don't fire subs with short barrels this issue may have gone unnoticed. My 12 inch barrel and subsonic round combo means less blowback pressure (I think) and then throw into the mix the BMA which was causing some form of impingement either between upper and lower, or directly onto the bolt carrier. The result was frequent failure to fire because the hammer did not reset, and the occasional unintentional two round burst. After about 50 rounds it was no longer a semi-auto.

Fix was removing the sharp parts on the top front of the BMA. It took a couple of attempts as I was cautious not to remove too much. But once I removed enough not only did proper cycling return, but the rear pin was easier to remove, and the upper and lower easier to close.

Issue 2. Mag retention - No matter what I did, even after fixing the issue above I could not achieve positive magazine release catch engagement. It clicked like it was retained, and felt initially like it was retained, but a quick mag check and out it came. I tried removing some sharp edges from the underside of the BMA to ensure the mags were up as high as possible, but this wasn't fixing the issue.

Fix was realising that the bottom rear of the BMA was connecting with the mag release and backing it out, enough to hit the slight radius in the polymer 15/22 mags so the mag could be pulled free. The picture in the mag well is after I've removed the corner. I'm now able to get positive mag retention and finally my L119A22 is running like it should with fully functioning LRHO.

In hindsight I wish I'd gotten the Kriss DMK22 bolt catch and some mag shims, but I didn't know what I didn't know!