Caster, no problem, I've done it and it's a neat conversion.
First, let's straighten out a few fallacies: You can make all the .357SIG cases you want from .40 brass. That's all we use here and we run many many thousands of rounds a year in 9x40 and .357SIG chambered Open IPSC guns. The factory SIG round is a tad longer and foolishly headspaces on the case mouth, but we set them up to headspace on the shoulder, as all other bottlenecks routinely do. I like about .006" to .010" headspace to make up for dirt in the chamber and that works well with the H110 Hodgdon or N110 Vihtavuori powder we use in the Open guns (mostly 1911 based). In a noncompensated gun like my CZ and 1911, I use a faster powder, so could get away with a tighter fit, but why fix it if it ain't broke? 2 layers of IPSC target tape on the head of a loaded round should allow the action to close normally, 3 should be a hammer it shut proposition. The tape is just about .004" thick. A good way to set up your dies.
You can take a 9mm barrel and open it up with a .357SIG reamer. I've never purchased a .357SIG barrel, and I've built a LOT of these. The slide needs to be opened up on a 1911, and replaced with a .40 Slide on a CZ/TZ if it starts as a 9mm. By the way, you can still pop in a stock 9mm barrel and run it quite reliably (and accurately) with the .40 slide and extractor in place. I have one with a .40, .357SIG, and 9mm barrel and all shoot very well with the same slide setup.
If you can't find a 9mm CZ barrel, those made for the TZ's can be very easily machined to fit. You don't have the little tab on the hood but it's not needed. I like barrels from Barsto, Storm Lake and Huening if you can get them, but in a pinch, just get a stock CZ 9mm barrel and rechamber it.
Recoil is about the same as a hot .40 load, noise is higher depending on powder type and amount, and the power is definitely there with 125's at over 1400 easily attainable.
People who tell you (sorry Jim) that one of these has recoil and noise levels like a 9x19 are dreaming. Simple math tells us these are hot loads but there's no problem loading down to say 1100 fps and these are a tad milder than the same velocity in a 9x19. A side benefit is that all the bottleneck guns (non-compensated at least) I've shot are deadly accurate, even ones based on factory stock not-fitted-very-tightly barrels. The natural tendency for the round to find dead center in the chamber can't hurt I guess. (In compensated guns we use up to 17 grains of slow powder to create the down-force we want, and the turbulence in the compensator means we lose a tiny edge in accuracy over, say, a .38Super otherwise identical).
I use Dillon carbide dies, but the steel ones from Lee and RCBS work well, too - you just need to keep the lubed cases extra clean so the dies don't get scratched. If you can't find a local gunsmith who can rechamber a barrel, or can't find a barrel, I can probably help. I'm in Canada so shipping is not a problem
Best of luck on the conversion. You'll like it.
Have a look at my website for further info -
www.armco-guns.comGunnar Christensen
