The variation of a rig in temp is good to minimise, and if you can't, learn what it does. As long as you're objective, you should see results from it.
One shooter I've recently worked with has reduced possible ranging errors just by changing the pointer so instead of it sitting over the wheel, causing problems with reflections, it obscuring other marks & having to remember if the range mark should be above it or on it or wherever, it now points only to the side of the wheel. Thus it points precisely to a mark on the wheel. Even with a few mm between 50 and 55, it's able to at least indicate a clear reading to the yard.
It might be worth considering working in yards. (or both) Although meters does have a certain amount of sense to it for trips abroad, working in yards means more points to look at... 10-55 is 10 targets in a field every 5 yds... 10-50m is 9. It can help because aside from this, if you know your max range for say 15's and 25's and standers/kneelers, and you trust the course setter, if your scope tells you these have been exceeded, you may get an idea of something going awry on a course. I've dealt with POI shift on a meter plinking range on a scope reading yards and it's a real head ache. With meters marked on a meters range it would have saved a bit of head scratching, and I would think vice versa. Dunno... the less I have to think about, the better for me... others may be different.
BFTA/NSRA County Coach
CSFTA Chairman/BFTA Rep