A challenge for you tinkerers
From what I understand, 9 round spring loaded tubes are used as magazines (I believe the seller made them from ten round tubes and a spring); so one can interchange them quickly without pouring in individual rounds. A total godsend.
While it's pretty hard to get a grasp on the mechanics without holding the gun; it looks like the gun has just been modded to accept 10 round tubes. It seems deceptively simple.
Thus, the challenge is creating the 9 round magazines correctly and finding out how they 'lock into' the marker. Man, I hope my gun doesn't get screwed up by trial and error.
Unless someone gets it up and running first, I'll be sure to make an instructable; and credit whoever helps me out.
Oh, the pictures the seller provided might prove useful, lol. And heres the manual for the USP
Its has great detailed info.....about the bolt mechanism. :|