Reloading .303 British : Velocity change due to Ambient temperature.

I will use these loads in February for an ISR event, that is being shot on reduced targets at 200m. This is st the Napoleonic indoor range, where we have our normal TAR ( Tir Armes Reglementaire) Service Rifle competition. Which is four weeks later. So I am using the ISR match as a practice match. I always have issues at this range, because the light is very different. The roof is partly open to slow the light in, and shadows on the targets.  My spotting scope is ok on the outdoor range, but I can never see anything in the black at this range.

I have a better scope on the way, so will be testing that as well.

In the TAR competition, we can only use the scope during the 5 test shots. Not during the match shots, until the round is finished.