I know the AR mags by Magpul function flawlessly in my rifle. I don’t use anything else. Ever.
I’ve started making 30 and 42 round bench loaders for Pmags in .223, and they are selling well. Next up is .300 blackout, and 7.62x39 (I have the mechanics on that one worked out, just pondering the production right now). Somebody today challenged me to make a 100 round loader for drum mags, so I’m going to mess around with that, too :).