In the closing stage of the war, nine of the Grossfuss Sturmgewehr prototypes were captured by the advancing Red Army; five of these were found at the Kummersdorf testing site.

(Horn spent most of his time in the USSR at factory Number 74, later known as Izmash, where other famous German weapons designers were held, including Hugo Schmeisser, etc.

[2]) Although the total number of Grossfuss Sturmgewehrs manufactured is not known, the numerous differences (noted by the Soviets) in part dimensions between the blueprints and the captured exemplars pointed to the experimental nature of the guns, suggesting that design adjustments were still being made.

The requirement to use blowback as principle of operation was interpreted as asking for a gun that was cheap to build, because it translated in a simple design with few parts.

[1] Although the existence of the Grossfuss Sturmgewehr and its basic principle of operation became known in the West in the decade following the end of the war, hardly anything else transpired from behind the Iron Curtain.

According to a 1958 book of the Army Ordnance Corps: The firm of Grossfuss in Dobelin produced a unique retarded blowback gas-actuated system, no specimens of which has ever been seen.

[3]A single, slightly incomplete exemplar remains in existence at the Military Historical Museum of Artillery, Engineers and Signal Corps in Saint Petersburg.