I just received a 1700P breech and parts in the mail today! Plan to modify my 2300KT with it. Here is what I have found so far.
1) The 22xx steel breech & 1700P breech are the same length.
2) When the ends are lined up, the rear sight slot lines up, but the cocking slot and transfer port hole don't.
3) There are dimension differences in the loading slot (knew there would be).
4) When the Marauder rifle barrel top slots line up with the set screw holes in the top of the 1700P breech, the back of the barrel is flush with the front of the loading slot. However, the transfer port hole in the barrel doesn't line up.
5) When the transfer port hole in the Marauder barrel is lined up with the hole in the breech, the back of the barrel sticks into the loading slot - probably about the same as the Marauder guns.
6) The Marauder rifle bolt assembly is too big for the 1700P breech. (Anyone interested in buying a .22 caliber, Marauder rifle bolt assembly [2263A102]?)
7) The pellet tray is machined from black plastic (delrin?) and is expensive ($17.85!).
I'll use a cut down Discovery tube for the air tube, so I'm glad I haven't cut the slots and holes yet. I have to figure out how much to move them.
If anyone is interested, I'll post pictures comparing the two when I take them.
I had thoughts along the same lines. So keep up the good work Tink, and I'd appreciate you posting pic's.