I use H414SL10 in my 6.5x55 summer and winter. I use it with everything from 95 grain bullets to 140 grain bullets.
In all honesty, I have never noticed any difference in pressures or velocity between -30 and +30 temps.
W760, is an almost identical powder to H414SL10. The regular H414 and W760, are virtually the same powder and the loading tables are interchangeable.
As mentioned earlier, magnum primers are the way to go with ball powders, especially the slower ones.
W760, H414 and H414SL10 are some of the most consistent powders on the market. They were the forerunners of the temp resistant powders so popular today.
If you are using magnum primers, I doubt there will be little if any difference in your POI.
That same statement can't be made for other powders though. Be careful. Just remember, a moose can't tell the difference between a bullet traveling 200fps slower or faster when it hits him/her.
Years ago, when estruded stick powders were the norm, and only a few ball powders, like BL-C were available, temperature sensetivity were the norm. It was a real problem but we lived with it and just tended to hold over in the dead of winter. That's all changed now. There reall isn't any need for it with the new powders available. H4831 used to be a real bugaboo in winter. I got into the habit of using magnum primers with all slower powders, I had a lot less temperature issues.
I really hate making up loads for summer and winter use. The summer loads may be safe in winter but the winter loads can have some serious pressure issues in summer.