A quick thought.
The Tula machinery and all rifles and parts were moved to Izhevsk when threatened by German forces advancing on Leningrad.
It is possible that the rifle barrel you have was made at Tula but scoped later at Izhevsk, who did not put sniper marks on rifles. I have two sniper marked Tulas that did not ever get drilled for scopes, plus a 43 hex Tula, so odd stuff happened.
As I said above, armourers certainly put scopes on in besieged cities and probably field armorers did also.
The refurb welds show it was descoped by the Soviets and refurbed postwar, so it's an "official ex-sniper."