I would be suprised if the Russians made it, they might have made some to store away with their captured Mausers, although they might have captured enough ammo to make that moot. Some eastern europeans made 8MM ammo while behind the iron curtain, but I know in at least one case it was made with steel cases like Russian or late German war ammo. What is the headstamp on the ammo? Cause it should be in Cyrillic characters if Russian made I would think.