UC
No, it's the .32 S&W short case.
OK - wish i had one of those conversions - i would like to try it in the U-mag - but I would need away to hold the shell in place until the hammer dropped - something like a 209 spring - would not have to be much.
Probably a pound heavier than the Umag with a laminated stock.
Ouch that is a heavy gun....