The ZK-412 (also referred to as SS-42) is a curious early assault rifle in a proprietary intermediate round, 8x35 rapid. It was developed between 1939-41 by the Koucky brothers in Czechoslovakia and presented to the Wehrmacht in February 1941.
It’s round is very similar to the 8x33 kurz. 8mm rapid was produced by Skoda for the ZK412 and a light machine gun called ZK-423.
I’ve read some interesting allegations that Polte ripped off 8mm Rapid for 8x33 kurz. They are similar but specifically not interchangeable. Rapid is longer than Kurz, and Kurz’s throat is wider.
Finally and most interestingly, there is allegedly a video of Kalashnikov citing the Kouckys as an influence on his design.
Most references to this gun are on Czech and Russian sites, any info is appreciated!
ZK 412 - experimental czech assault rifle * made in czechoslovakia
- designed 1939 by Josef Koucký & František Koucký
- manufacturer was ZBŠkoda
- produced from 1939 — 1942
- ≈ 24 were built
- assault rifle
- used cartridge: 8mm Rapid with a muzzle velocity of 680-720 m/s
- rate of fire: ≈ 700 - 750 rounds/min
- uses a 30-round detachable box magazine
- mass was 10.6 pounds (4.8 kilograms)
- length was 3.22 feet (98 centimeters)
- barrel length was 1.37 feet (41.8 centimeters) 8mm Rapid (Zbrojovka Brno) : Puškové metrické