I find the commercial ammo generally shoots low compared to military light ball. As in, oh, about 6 inches or so low at 100 yards. I've actually worked out kind of a rule of thumb on sighting that so far seems to be holding true.
If the rifle is zeroed on military light ball, then setting the rear tangent to 300 meters will be fairly close to zero for commercial ammo.
Your mileage will almost certainly vary.
The reason why (I've heard, anyway) that the commercial ammo shoots low, is that with 120+ years of guns, in wildly varying conditions out there, that shoot 54R, commercial ammo makers err on the side of caution and load the ammo a lot cooler than the military spec ammo, for safety reasons.
Other than that... Ram the ammo home and pull the trigger. A 1930 hex receiver Mosin will take far more abuse than you can imagine.