As mentioned above, you just sight in so your impact is always the same distance apart from point of aim, as the scope offset. So it doesn't matter what the distance to the target is, you will always be hitting 1.5" (or whatever) from point of aim.
The other thing to remember is that most sniping was done at fairly short ranges during WW2. I remember watching an interview with a WW2 sniper, and he said that he rarely took shots past 200yds with his M1d, and never past 300. The Garand sniper rifles were quite adequate for these ranges, but in truth were not great as sniping platforms go.