I have read on various forums that both 7625 and 4756 may have ignition problems in very cold weather. Never willing to accept this without conducting a controlled test I place half a dozen loads of each powder in the freezer for a week. I though that was plenty long enough
I then grabbed the frozen shells, walked into the backyard and fired them. While I was not set up to measure pressure or velocity, I did not not detect any difference in recoil from the same loads that were not frozen.
My hypothesis to prove was that 7625 would produce less recoil (squib load) when frozen. My finding for my rather limited test was that loads with 7625 were not affected at kitchen freezer temperatures.
For what it is worth,
Mark