The ZB47 was developed at Brno as a contender for Czech military submachine gun adoption in the late 1940s. The Czech Army had technically adopted a submachine gun prior to World War Two (the vz.38; video on that is coming a bit later) but production did not begin before the arrival of German troops. After the war, the Army was eager to add a submachine gun to its arsenal, and the vz.38 was no longer a practical option as it was chambered for the 9x17mm cartridge.

The ZB-47 is chambered for 9x19mm Parabellum, fired from an open bolt, uses a simple blowback action, and does not have a semiautomatic setting - just full auto. In its infantry configuration, it has a fixed wooden stock with a thumbhole design and a 72-round (!) magazine fitted almost horizontally under the stock and barrel. A unique feed system pushes cartridges vertically up out of the magazine feed lips into a pair of feed ramps that pitch the round 90 degrees forward and into the chamber. The system is closest to that of the FN P90, although the cartridge rotating element on the ZB is built into the gun, not the magazine. The paratrooper variant of the gun has a collapsing metal stock, which shorted the overall length and also restricts its capacity to a 30-round magazine when the stock is closed. Rate of fire was reportedly a blistering 1200 rpm.

One challenge of this very long straight magazine was the slight taper of the standard 9x19mm cartridge case. In 30-round magazines this is not really an issue, but by 72 rounds the taper adds up to enough to cause problems stacking cartridges. Brno attempted to solve this by making a truly cylindrical version of 9x19, but the Czech military was (rightly) not convinced of its benefits and rejected it.

In the 1947 field trials, 8 Czech units were given examples of the ZB47 and other competitors. Five of those units actually reported favorably on the ZB; it looks like a very awkward gun to handle but actually isn't in practice. However, the Army deemed it to have too many drawbacks, including the magazine reliability, poor accuracy, and bring judged too fragile. One more set of trials would take place the next year and ultimately the CZ model 23 was adopted. In total, just 62 examples of the ZB-47 were produced.

Many thanks to the VHU - the Czech Military History Institute - for giving me access to these two fantastic prototypes to film for you. The Army Museum Žižkov is a part of the Institute, and they have a 3-story museum full of cool exhibits open to the public in Prague. If you have a chance to visit, it's definitely worth the time! You can find all of their details (including their aviation and armor museums) here:

https://www.vhu.cz/en/english-summary/