Did the Soviets follow the standards set by the C.I.P. ?
Was every barrel proofed in the white, prior to assembly-- a la black powder proofing-- and then test fired again after final assembly with overpowered cartridges?
Or did the Soviets perform test firing on sample batches of finished small arms?
I don’t think there’s going to be a definitive answer Boris. The Soviets were pretty serious about the quality of their arms industry so I can’t imagine they wouldn’t have proof tested and zeroed each and every one, but I’ve got nothing but intuition to back that up.
I do remember reading long ago that it was thought there were common ‘proof marks’ on the left side barrel lug (circle with a TK comes to mind, or maybe it was a circle П, honestly could be almost anything I suppose).
If every rifle was test fired after assembly, they would have to be cleaned due to corrosive ammo.
The barrels on Chinese sks bear the Soviet proof marks long after the sino-soviet split. Romanian M59s also bear known soviet proof marks.
I've long thought this to be strong indication that pressure testing -- at least for the soviet sks bbls-- was done prior to assembly.