In 1966, CZ undertook Project PRAK (“Slingshot”) to investigate the possibility of converting the CZ50 pocket pistol to 9x18mm Makarov. The PM Makarov was adopted in the 1950s and used throughout the eastern bloc, but not in Czechoslovakia. A normal CZ50 pistol was taken from the production line and fitted with a barrel from a vz65 Skorpion (that’s the model made experimentally in 9x18mm).
A new magazine was fabricated, using the follower from a .380 Walther PP magazine. The only change to the slide was opening the breech face for the 9x18mm case. The only other modification was simply the replacement of the barrel.
Firing trials involved 3500 rounds in the gun. After a few initial extractor problems, it ran well until after about 500 rounds the hammer was visibly peening the back of the slide. The rear of the slide was milled down and rehardened and testing continued. At about 2000 rounds the magazine body cracked, and it was replaced at about 3000 rounds. At 3100 rounds the firing pin broke, and was also replaced. The conclusion from the testing was that a converted CZ50 pistol would have a lifespan of about 2000 rounds. The conversion was never actually put into production, though. At the time, the Czech military pistol was the vz.52 and the CZ50 was used by police. In 1982 the military adopted 9x18mm in the vz.82 pistol, and never needed to convert existing police guns.
Thanks to the Czech Military History Institute (VHU) for graciously giving me access to this one-of-a-kind prototype to film for you! If you have the opportunity, don’t miss seeing their museums in Prague:
https://www.vhu.cz/en/english-summary/
“Down-calibering” a pistol design, as CZ did with the Nickl-designed 9 x 19mm prototype in creating the vz.22 and vz.24 9 x 17mm (.380 ACP) pistols and the later vz.27 blowback 7.65 x 17mm Browning, generally works very well. Reducing stress on the mechanism generally pays dividends in terms of service life and functional reliability.
But “up-calibering” a design to a cartridge with higher stress factors almost never works unless the design was greatly over-engineered to begin with. Successful examples of this are rare, in fact the only ones I can think of offhand are the Spanish Campo-Giro and Astra series (9 x 23mm and 9 x 19mm) And the various Hi Point blowbacks in assorted calibers from 9 x 19mm to most recently 10mm Auto.
Going from 7.65 x 17SRmm Browning to 9 x 18mm Makarov was probably a perfect example of why it generally isn’t worth the effort.
clear ether
eon
This test worked pretty well it seems.
Few thousands round were the lifespan you could expect from a pistol back then. This one, after the slide had been slightly reworked, didn’t have problems at the slide and frame any more. The magazine and firing pin are replaceable parts that weren’t supposed to last as long as the weapon.
I must note that some cartridge were designed specifically to up-caliber existing fire-arms. .45 GAP https://americanhandgunner.com/handguns/the-rise-and-fall-of-the-45-gap/ was with 9×19 mm Glock automatic pistols in mind. .41 Action Express https://www.iwm.org.uk/collections/item/object/30027429 was conceived to make Uzi converting easy.
Caliber conversions in any direction, up or down, are fraught with issues. I will admit that it’s a lot easier going down than up, but… Even so, the problems that come along with that are just as hard to overcome.
Taking the 9mm Glock frame to .40 S&W was problematic in the extreme; trying to do a home-brew down-conversion of the Glock 21 to that same .40 S&W was just as much of a nightmare. Feeding and magazine issues galore, and my buddy who was trying it finally just said “Screw this…” and did it with a Glock 20, which proceeded to present some of the same challenges, although he did manage to finally make it work.
Caliber conversions are generally easy to do in single-shot or revolver-style weapons; you add in feed mechanisms, and you’re just asking for trouble.
“(…)1966, CZ undertook Project PRAK(…)”
Few year earlier in Polish People’s Republic CZAK designed P-64 https://modernfirearms.net/en/handguns/handguns-en/poland-semi-automatic-pistols/p-64-eng/ which fired 9×18 cartridge. It was new design and become service automatic pistol in that country, thus being another example of WarPact member deploying automatic pistol other than PM. Note that P-64 was actually lighter than vzor 50.
Also the Hungarian FEG PA-63 and R-61, 9 x 18mm versions of the Walther PP and PPK respectively.
The ones I had were quite accurate, functioned very reliably, and the 9 x 18mm round delivers roughly the energy of a .38 Special 158-grain “police” load.
As you might expect, they both had a memorable “kick”. Especially the diminutive R-61.
clear ether
eon
Surely they must have changed the recoil spring!