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I it possible to convert a CZ75 Cadet .22, to a 9mm?
The Kadet Pistol has been discontinued. FWIW, it was significantly more expensive than the standard pistol (MSRP of $690 vs. $499 respectively.) So now the Kadet Kit is the way forward.
If you have a dedicated Kadet pistol, you will need to call CZ (Toll-free: 1-800-955-4486,Phone: 913-321-1811) and ask what it will cost to order the parts needed to build your own 9mm conversion kit. The few dealings I've had with CZ (and Dan Wesson) CS, I've found them helpful.
IIRC, you will need: Slide, Barrel, guide rod, slide stop and recoil spring. I don't know if there is any required fitting of these parts. I know the reverse of the process (9 mm to .22 lr) may require some minor initial fitting of the kit, according to the instructions with the kit. FWIW, I have a CZ-75BD and a Kadet kit. The kit worked great, without any fitting in my case.