During USSR period there are just few groups of people could own rifled guns: commie bosses, military high staff, proffi hunters, native Russians at Far East and Far North who hunted for living.
The rest of people had to bring rifled barrels they owned or found to police for desroing them or for de-activating (drilling, overboring or filling up with melted lead).
This drilling liberated from Germany is one of them.

Geno.