I've copied some emails between myself & Black Dog Machine regarding their X-Form Mags & your BHOA.
I've done some editing to make it somewhat clearer to all.
This was 4 years ago. It seems like everyone abandoned this except for me!
Me. Currently, with a CMMG Sierra Upper with the BHOA installed, 25-rd X-Form Mag w/SS feed lips won't even feed rounds with the bolt actuated manually.
The CMMG Evolution mags feed properly. I don't expect the BDM to lock back the bolt & hold it open with the mag removed, but they will only function if the BHOA is removed.
BDM. That is correct, our mags will function if the BHOA is not installed. (Note: BDM changed this after my testing)
Me. CMMG refers to it as the BHOA (Bolt Hold Open Actuator) & I can verify that it does not work.
They do have a new Actuator for the BHOA, which may or may not fix this issue. (Note; CMMG used to have a video showing this).
The only difference is the 2nd gen has an angled tab.
BDM. I emailed CMMG- they told me our mags will work but they will not activate the BHOA.
Me. I solved the problem myself.
You must have the CMMG BHOA Gen2 actuator for proper functioning with the SS feed lips of the X-Form mag.
I modified my Gen1 by cutting a 60deg angle with my Brownell's 60deg dovetail file.
Without this angle, the rim of the case gets caught under the tab of the actuator & the rounds don't feed at all.
Been an amateur gunsmith for 25 years & an engineer for longer.
Proof that the CMMG BHOA Gen-1 actuator is no-go with the BDM X-Form mags. At least, they didn't make the Gen1's for very long.
BDM. I appreciate you letting me know. It's been a big question for a few months now.
Me. The new followers had no noticeable effect on functioning with the modified actuator.
Of course, I modified the actuator before the new followers arrived.
Don't know what the new followers would do with the old actuator. Haven't tried any live rounds yet, hopefully this weekend. (Note: they worked).
SUMMARY
There are 3 functions that need to be made clear. This seems to be missing from every YouTube video & every forum post on all forums.
1. AR15's hold the bolt back after the last round.
2. When the mag is released, the bolt stays held back (i.e. bolt remains open).
3. Insert new full mag, depress bolt release, round is chambered.
Most, if not all, AR22's perform #1, but not #2 or 3, which is the true function of the BHOA & the Evo Mags.
The BHOA can stay installed no matter what mag is used.
The only mags that will hold back the bolt after the mag is removed is the CMMG Evolution Mags.
Their other mags (CMMG grey ones) function just like yours (BDM's), they hold the bolt open after the last round, but when removed, the bolt will close.
With BHOA & Evo mags, functioning is identical to that of AR15 w/5.56 mags, i.e. bolt stays open after last round fired, remove empty mag, insert full mag. depress bolt release, no need to use charging handle.
UPDATE
The only real difference in the mags, is the Evo mag follower is a bit longer in the rear than the BDM mag. It would be nice if BDM copied the Evo mag follower.
I've given up on any new .22 stuff from CMMG.
I'm going with the Boonie Packer Better-Mag adapter and S & W mags.