My concern is more about velocity spread than velocity loss. If I lose 50-60 fps from a good summer load at 80 - 90*F to winter temps of -20* to + 15*F, that's no big deal, at least to me, if it's still accurate with an ES of not more than 20 fps.
I find that WLRM primers help provide that consistency for me in addition to the powder used. RL-15 is a good powder for that as is RL-17. RL-22 and 19, in my experience, are awful in that regard.
But, as I mentioned above, if I add an extra grain or two for winter hunting in the same rifle, I'll go back to the summer load when spring arrives.
In .45-70 and .458 WM, I changed to Hodgdon powders a few years ago using H4198 in place of RL-7 in each for bullets to 350grs, and even 400s, and H335 for any thing heavier. Both H4198 and H335 are very stable and consistent using hot weather loads in winter. Also, H4895 does an excellent job as well. I don't use IMR powders any more even though they are a Canadian product
