In REAL life with real snipers in the real world, wear the wear and backlash you speak of simply doesn't happen. It might at the sniper school where the telescopes are constantly being adjusted and readjusted by trainees during their courses - as the sniper div Instrument tech Sgt Neil Xxxxxxx will confirm.
But once the rifle is zeroed in they just don't get the constant adjustments/wear. They stay as they were set. There are two anti-backlash methods in the Mk1 and 2. The double springs astride the deflection cursor operate in both R and D mode whereas the spring in the base of the grat block (use a No4 backsight clicker spring....) only operates in the range mode. In real life, backlash in the deflection mode is the most important to eliminate.
Indeed, in the Mk1 and 2's there is an inbuilt method of adjusting backlash between the lead screw and the lead screw nut so there should be no problem there.......
Grease (or other crud) on the lens...... Advice for all, even the experts out there...... wipe clean with a clean piece of the cheapest kitchen roll as it contains little chemical/bleach/additives. New piece and clear residue with a degreaser. New piece and clean lens with methylated spirit several times, using a clean sheet of roll each time. NEVER, never but never ever use the same piece of kitchen roll twice and never, ever, never use anything else, such as a but of flannelette, dirty handkerchief of any other kind or cloth. When I used to repair them (no so don't ask.....) I used to use approx half a kitchen roll per telescope