Just conducted a test this morning. Back in the summer I did some load development with Reloder-22. It was accurate and with 55.5 grains pushed the 225 ELD-Match bullets to 2575fps. The temperature was about 90*F and humidity was about 85%-ish.
When I saw how cold it was going to be, I decided to test how much velocity would drop. I loaded up four rounds in the same brass, same primer, same bullet, same charge. Left the ammo and the rifle outside all night. This morning it was about 6*F and 65% humidity. I fired the four rounds over the Magnetospeed. My average velocity dropped to 2475fps, with an ES of 40fps. Yikes. RL-22 is out of the running I think. 100fps drop seems like a lot.
It's supposed to hit 4*F tonight, so I'm going to load up a few rounds with Superformance and see how that one does.
The other powders I'm trying are H4831SC, IMR-4955, and H1000. What are other's experience with these powders? Or are there others I should be looking at?