As far as I know, bullets do travel faster in warmer weather generally. This is mostley due to the air being thinner and having less friction in warm climates thought. I don't think you can safely assume that the temp has the only influence on muzzle velocity though. I am sure temperature will impact a little. Some powders are more vulnerable to temperature differences than others too. I would guess that it has more to do with your chamber dimentions, rate of twist, seating depth, and throught of the rifle that you are shooting verses the those charectoristics of the test barrel.
but I could be wrong too lol! good luck
I used to re-load but now I "hand-load".
-- Well, at least I try