Mine is hiding in the safe. Installed the Glock magwell and caught a sale on Magpul 20 round Glock mags. I also removed the rear sight, installed a scope base from an 336 Marlin and topped it with a Tasco ProPoint. Wicked fun little carbine, accurate and cheap to shoot!
Well mine is a fun plinker, but velocity increase over my 3" barrel SIG is a bit less than 200fps, not the ~600+ that one would expect. I haven't tried the new Federal ammo for PC C yet.
The 9mm versions are available around here! So are the 40 versions-they aren't selling.
As for a magwell for various other magazines, can you hold your breath a really long time? The 45 ACP would make a really good HD gun and possibly competition but not hunting. The 10mm would be a lot better choice.