I really love this adapter, but one of the best features does not work: the bolt hold open. This is using a CMMG conversion kit, a CMMG 22 barrel, and a mil spec upper receiver.

I am in contact with Redi-Mag. While they are very helpful, nothing suggested has worked. The bolt catch will move freely without an upper, but requires leverage with a screwdriver to operate if an upper is attached. I have lubricated the adapter generously and am unable to find any sort of obstruction or explanation for why it is sticking. I have tried two different lowers from different manufacturers, so it most likely is the adapter or the upper. Thanks for any suggestions.

Semi auto or auto application? (known issue with the auto trip, if trying to use it with auto).

Also possible you're not pulling it back far enough for the bolt catch to properly engage - this can be caused by the spring bunching up and binding at near-full counter battery stroke.  There's a fix for that, too.

Can you look inside the ejection port when trying to engage the BHO, and see if the bolt is in fact withdrawn far enough for it to clear the front of the bolt face?

Thanks for the reply. This is semi auto only. I am able to pull the bolt back far enough to engage the BHO, but it takes a screwdriver under the bolt catch to make it work. It seems like there is a lot of friction on the parts, but I can't figure out what is causing it.

I had clearance problems with the "elevator" piece that engages the bolt hold open... one receiver it worked fine, one it was tight, and through a few trials, discovered if the unit rocks slightly the engagement piece can drag on the rear of the mag well.... a slight clearance pass with a sanding drum fixed the problem...be sure you engage the center cut out section of the slider with the bolt hold open arm

Thanks. What part of the elevator did you sand exactly? I'll take a closer look at that area and see if I am having the same problem.

the part that extends through to the rear of the adapter, and can touch the mag well itself....check by rocking the adapter fore and aft

Thanks. I'll take a look.

Google brought me here.  Looks like I'm having the same problem.   The slider is being pressed against the rear of the mag well.  If I leave the pivot pin out, the bolt holds open fine.  Of course, I can't leave it like that so I'll grind a little bit off of the slider.

ETA: On second thought, after hand cycling the bolt a few dozen times, it's working a bit better.  Both the CMMG upper and the Better Mag adapter are brand new.  I'm going to run a brick through it first to see if it'll loosen up and fix itself.

I hope yours works. I've probably put a brick through mine and it is no better. Redi mag offered me a full refund, while excellent customer support, isn't what I wanted from them. I will try grinding the bolt catch adapter down a bit when I get some free time; hopefully next week I can update this with good results.

Took if to the range last night and ran ~200 rounds though it.  The bolt held back successfully every time - but the lever wasn't being actuated all the way - just enough to stop the bolt from moving forward.  Good enough for now, but it's hard to tell if the hold open is working just by looking at the paddle.  Also don't get that satisfying feedback from releasing the hold open by pressing on that paddle.

If I take the bolt out of the dedicated upper and throw it in my regular 5.56 upper, it works just great - so I can't really fault RediMag for the BetterMag not being able to work perfectly out of the box on every possible platform.

Probably will finish off the brick and run another through.  If it's not fully loosened up by then, I might shave a little off the backside of the slider with the Dremel.