Yes if a load of 25.5 gr works great in spring summer it will vary in the colder weather, usually slower velocity in the cold if using a summer load. Varget on the other hand is way more stable. I live in az and just load h335 at 24.5 for plinking and can notice the difference from summer to winter and I don't have a crony
About how much of a difference in accuracy ? Is it enough that I should stop with the H335 and work up a load using Varget or another powder ?
H335 in a load of 24.5 is extremely accurate in my AR 15 with a 55 gr bullet.