Been having some issues with H4831SC out of my .260 Ackley. The weather has been weird here the last couple weeks and will be in the low 60's one Saturday and mid 70's low 80's the next. The problem I'm having is when the temp warms up my point of impact changes by about 4" on the low side which is the opposite of everything I have experienced when temperature is concerned. The weather here in AZ can be quite drastic as far as temperature swings go and the main reason I wanted to use a powder that wasn't supposed to be so temperature sensitive. When shooting in the cooler weather my come up numbers are right on and when warm I have to add a minute to each number out to 400 meters and 1.5 minutes at 500 meters. Any one experiencing this type of problem with this powder? Am I asking to much of a powder to be able to handle 20 degree temp changes?

My particular barrel seems to prefer velocities on the low side which I am ok with since it shoots so good.
42 grains H4831SC
Lake City Match Brass
140gr Berger VLD
2740 fps
S.D. of 3 (wow)
and groups consistently under 2" at 500 meters.