As stated above, Ruger makes the best 20-Rd mags for their Mini-series of carbines, so it's better to just pay the extra bucks and buy a Ruger mag to start with................As to the "Pmag" question, I'll assume that by that we are talking "Pro Mag". And if so, the only Pro Mag that I know of worth fooling with for a Mini-30 is their 10 Rounder, and even that one needs to be took down, de-burred, and polished inside. Lately, some have been furnished with springs that are way too strong, and if you happen upon one of those, you'll need to remove one full coil off of it's length or it's not going to function right if fully loaded. Personally, I wouldn't even fool with an off brand 20 Rd mag. Send it back for a refund, that's my advice.
DGW