That rifle is not just a run of the mill .303 Brit. Length and weight seem to indicate some special purpose built- long range target gun perhaps. Use a diopter sigh would support that. This is a special gun.

Is that a factory barrel? Are there any proof marks on the barrel? Muzzle is not crowned? Barrel length-inches? What is the diameter of the muzzle, 1 inch? A gun of that era shouldn't be metric and and metric measurement won't make it easy to identify. Any inch measurements might conform to purpose and literature of era.

Action could be metric measure however if sourced from Germany. Action looks to be a Mauser pattern.