The 7.5x55 case is a very good design.
It is just very slightly better in many ways than the 7.62x51. Not enough to encourage anyone to go to the expense and effort to build or rechamber an existing rifle.
When it's utilized in a modern, strong, bolt action rifle, it will easily duplicate 30-06 loads with bullets up to 180 grains. The 30-06 gets the edge with heavier bullets.
The 7.5x55 is short enough to fit into short actions with 150-165 grain bullets, and generates 2-4% more velocity, depending on the rifle
It's a very efficient cartridge.
As to the OP's question.
Slug the bore on your rifle.
These are very well made, mass produced military rifles. Tolerances were followed very closely but there are some variations in bore diameters.
I've had them with both tight and loose bores.
All of them, even the Cadet rifles shoot 30 cal (308) diameter bullets well.
I've measured at least a couple dozen bores of Swiss Cadet, M1896/ M1911/ K31 rifles, they are possibly the most consistent of any other milsurp s I've measured, between rifles, including the Swede M96 and variants.