https://youtu.be/gnDE-3kEaVc
The ZK-383 as it is known today is a side-magazine SMG with a bipod, but that is not how it began its life. The gun was originally designed for Czech military trials in 1938, which it lost to the vz.38. After the trials, the factory looked for export sales, and found a potentially interested party in the Bolivian Police. A batch of samples were made in anticipation of a larger contract, and this is one of those samples. It is a simple blowback gun with a double-feed magazine and removable bolt weight to adjust rate of fire. The sale to Bolivia was interrupted by the Wehrmacht marching into Czechoslovakia, and the gun ended up undergoing further iteration before being produced under German occupation as the ZK-383 we are familiar with today.
Thanks to the Czech Military History Institute (VHU) for graciously giving me access to this very rare 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/
vz.38 SMG video: https://youtu.be/NPBzN2-6zh0
Attempt of opening https://youtu.be/gnDE-3kEaVc results in video not available.
https://www.youtube.com/watch?v=BMKSI31-E2s
This one works.
Spring in stock was earlier used in Steyr-Solothurn S1-100 https://guns.fandom.com/wiki/Steyr-Solothurn_S1-100
Externally this weapon is similar to later UD M42 https://modernfirearms.net/en/submachine-guns/u-s-a-submachine-guns/ud-m42-eng/ with both having vertical grip and rifle-like stock, but U.S. one having said grip in front of magazine rather than around magazine.
Providing police with full-auto-only sub-machine gun in 1930s seems odd. Did anybody outside Bolivia did this in 1930s, if yes where, if not why Bolivia was special in that regard?
United States and Germany, for example.
As as far as Germany is concerned, after WW1, not only civil war conditions erupted at a number of places, but also violent crime became a serious problem. Due to the Versailles Treaty, Police was the only government body that was allowed to have SMGs guns.