Originally Posted by BrentM
So now that I am thawed out and running the numbers it looks like 3600 is the correct speed to give the right solution at 500. Is it possible to see 200 fps variance in a 45 degree temp swing?
That comes out to around 4.4 fps per degree of temp drop. Thats not impossible, but you'd be better off double checking. I really don't know anything about that powder.
Put some ammo inside your clothes close to your body for a good while so your powder temp can get close to 90 and do the same test to see where the group impacts.
That will give you both a broader temp swing, and a second confirmed drop at a known range...which seems to be the variable you're missing to know for sure if the data is reliable.