I had a CZ50, but never really investigated removing or replacing a barrel in a CZ50 or CZ70, which is almost the same gun.. The slightly newer blowback CZs, like the CZ82/CZ83, and the vaguely similar Soviet Makarovs had barrels PRESSED into the frame, and I think a similar device must be used to remove the barrel. Those guns did seem to have a pin in the frame that MAY have helped hold the barrel or make the fit tighter.
The detailed gun drawings I've got for the CZ50 don't show a pin used to position or hold the barrel in place. My drawings of the CZ82-CZ83 show what seems to be a pin beneath the barrel, but that pin isn't numbered in the parts list and it's quite small. It may just be that the pin isn't meant to be removed -- that it's just there to add additional tightness to a pres--fit barrel.
I have an old copy of American Gunsmith (dated October 2008) which addresses disassembly (including detail disassembly) and reassembly of the CZ70, and it just doesn't address how to remove or install a new barrel. (There are a lot of warnings telling you to detail strip the gun inside a large (clear) plastic bags, as a number of small springs will fly out if you're not careful, and finding them again may be an almost impossible task (as would be finding replacements). (The American Gunsmith booklet showing disassembly and reassembly of the CZ82/CZ83 (dated April 2008) also does not address removing or reinstalling a barrel.)
Someone at CZ USA might know, for while CZ USA never handled the CZ-50s or CZ-70s, they might know what was required to do a barrel change in the CZ82/CZ83.
