Provided you have a fair idea of what's going on and use a low pressure round like a .22LR with subsonics there isn't that much risk. Especially if you use real barrels or even pick up some cheap $5 junker at a gun show that you can salvage the mag, and barrel from (Maybe the trigger or at least parts of it too).

edit: and just to throw it out there, .303 and 7.62x54 Rimmed share the same bore size as the .32ACP pistol round, and you commonly see SMLE and MN barrels for pretty cheap, all you'd need is a chamber reamer ;) . However you'd probably have to make your own mags since i don't think high cap .32ACP mags exist.

I'm pretty certain the old CZ Skorpion came in .32ACP.

That would be correct.

However if I remember correctly some models were chambered for other cartridges.

That would be correct.

However if I remember correctly some models were chambered for other cartridges.

Such as the .380 ACP.

Such as the .380 ACP.

Or even 9mm Mak and 9mm Para.

Oh, and on zip guns don't do it. Its a bit dangerous. The only zip gun I've seen work are the one shot shotguns made from old 3/4" steel seamless pipe. And they do blow up after some use, so no.

Provided you have a fair idea of what's going on and use a low pressure round like a .22LR with subsonics there isn't that much risk.

Just a quick note on this. Pressure isn't what's important, force is. For example: SAAMI specs say that a 22LR has a max chamber pressure of 24000psi, whereas the 45ACP has a max of 19000psi. However, the bore diameter of the 45ACP is about twice as large as the 22LR. If you do the math, you'll find that the force pushing back against the bolt face of a 45ACP is FOUR TIMES that of a 22LR.

Moral of the story: low pressure cartridges aren't always the safest.

It wouldn't have anything to do with the bore size would it? the .45 slinging a projectile almost 6x the weight and close to the same velocity would be that cause for that.