>>538081323
ZK 381 Au II was trialed along with the SVT apparently
>In the spring of 1938, the arms factory was visited by a Soviet military delegation. Among the weapons on display, Koucký's self-loading rifle ZK 381 caught their attention, and they expressed interest in its conversion to the Soviet 7.62 x 54 R (7.62 mm Mosin) cartridge. The Soviet side supplied the arms factory with 30,000 rounds for internal tests, as ammunition of this caliber was not produced in Czechoslovakia at the time. The arms factory produced two samples, one with a non-removable magazine for 5 rounds and the other with a standard, detachable magazine for 10 rounds. The samples were designated ZK 381 Au, with the additional designation being the internal code used by the arms factory for the USSR.

there are probably other trials rifles they could shove in
but I just meant the SVT suppressor