OK, I have also heard the cautions about H335 when I was planning to use it in my 45/70.
Soooooooooooo, I loaded up some of my hunting loads, put them in my up right freezer for a couple of days, then on one of my early morning shooting/testing sessions I quickly removed the ammo from the freezer, and packed it into a cooler with ice packs.
Went to the range, set up and then removed the ammo one cartridge at a time from the cooler/ice and fired each round over the chronograph and into the 100yd target.
The results ------------ barely any velocity loss and compairable groups with non- frozen ammo.
From my limited testing I can see nothing even close to a problem with cold weather use of H335.
Keep em coming!
Crusty Deary Ol'Coot