Chris,
In cold weather I don't think there is a huge problem with lube contaminating the powder if no over powder wad is used.

I do use over powder wads, either a thin "milk carton" wad punched out, or better I think is a thin over powder punched out of "Bee Brood Foundation" ……just 100% beeswax. The bee brood shields the powder from the more greasy/oily lube, yet melts on firing to allow mixing of the lube and hot powder gasses.

I use an arch punch reamed/drilled out to the needed diameter for making over powder wads. It is also possible to find arch punches in the necessary diameter in Metric (do the metric to decimal conversion). It so happens that a 13mm punch is perfect for .50 cal wads.

So many variables to try/test in search of a load that the rifle likes.

- Mike