Bob... I'm primarily a competition oriented shooter, and for about 3 years we held a monthly 3 gun match that used .22lr for the long gun, with center fire pistol and shotgun... that way we could shoot some light weight steel targets originally designed for the Sportman's Team Challenge, and be shot on a range designed for pistol use
my CMMG conversion unit started with the drop in chamber insert for a 5.56 barrel, and a couple thousand rounds were shot in practice for the Ft Benning 3 gun matches... after a couple of years, I opted for the dedicated CMMG barrel to improve the accuracy...when the competition shooting began, the overlooked problems with the conversion unit and magazines showed up... a broken extractor was replaced with a TACCOM unit, as was the recoil spring...without a dedicated bolt hold open, the follower of the Black Dog, CMMG OEM, and Brownells mags would catch the bolt for a last round hold open, and this started causing problems... the best of those magazines for me were the X Form from Black Dog (edited) with the metal feed lips...
I noticed that friends shooting the SW 15-22's did not seem to have the magazine related problems that I incurred, so I tried one of their mags, and it shot well, just rocked a little in the mag well... when I added the Boonie Packer Better Mag adapter to the mag well, the rocking stopped, and it has a linkage that allows the follower to raise the last round bolt hold open on the AR lower... if you load individual rounds, and release the follower to seat each cartridge, the noses will alternate in the mag... since using that technique, my 15-22 mags have been very good performers...the 15-22 mags use a controlled follower with a fan fold spring, while some of the others use a coil spring that allows more tilt to the followers
from 95-99 I shot the STC with a custom 10/22 which was limited to 10 rounds only in a magazine... the rotary magazine in that configuration was flawless for a bunch of shots... and I learned a lot about 10/22 triggers.. that is why I made the comment about the 10/22 rotary mags vs. Atchisson style mags.... if you have any Steel Challenge competition in your area, you might ask around about the reliability of the .22lr long guns... regards
I have a takeoff 10/22 barrel that may get chopped if I want less than 10", but I envision a Charger that looks like a VZ61 Skorpion in .22lr with angled fore grip and 25 round mags for about $325... I think you may have started me on my next project... regards