The URZ (Univerzální Ruční Zbraň, or Universal Hand Weapon) was a 1966 project designed by Jiří Čermák (designer of the vz.58 rifle). He envisioned a weapons system family with largely interchangeable elements that could be configured as a service rifle, carbine, light machine gun, vehicular machine gun, or precision rifle. The Czech military was not interested, but Čermák was able to convince the government to allow its development for export instead.

The design is a delayed-blowback system using rollers, and belt-fed. The first few examples were made in 7.62x39mm, but development switched to 7.62x51mm NATO in a rather surprising move. Presumably this was intended for sale to unaligned nations who were interested in the NATO cartridge, but still - seeing its development in then-communist Czechoslovakia is pretty unusual. Ultimately only 9 examples were built before the project was abandoned.

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/