As far as temp sensitivity, it can be a valid question. Where I am if I work a load up in the winter it might be 10-30F. In the summer, 80-100F. Went to college in Florida up in the man handle. winter temps got down into the 30s. Summer was generally in the 90s and up. And if you have ammo sitting in the sun it can get mighty warm.W231 Temp. sensative.... I load at sea level @ ` 75F. I've shot loads @ 4800' and @ 118F (Past Barstow Ca.). Too many put too much B.S. into temperature sensitivity w/o understanding the high / low of the actual question.
Unless we are talking Arctic / High Southern Desert dichotomy too much emphisis is put on the subject at all but the most most extreme ends of the load data. Some Ball Powders need an extra hot flame to ignite at extra cold temperatures.
i.e. All Ball powders require Magnum primers. Absolute pure B.S.
Found this here https://www.thehighroad.org/index.php?threads/powder-less-affected-by-temperature.804961/
Standard/Temperature sensitive powders (produces higher velocities at higher temps):
- Clays
- Titegroup
- W231/HP-38
- Power Pistol
Reverse/inverse temperature sensitive powders (produces higher velocities at lower temps):
- Competition
- WST
- Solo 1000
- N320 (but some claim reverse temp sensitivity)
- SR7625
- Universal
- WSF
- Silhouette
and this here https://www.tapatalk.com/groups/idpaforum/winchester-231-t4998.html
If you're going to shoot 231 in a cold weather match (in Florida that means 50 degrees or less) don't count on your velocity figures taken at 75+ degrees holding up. Win 231 will wimp out in cold weather. It is very temperature sensitive. I've chronoed loads at 72 degrees from a .38 revolver, and picked up 85 fps at 90 degrees... and lost 75 fps at 50 degrees.... same loads from the same batch, same gun. If you develop a load at 80+ degrees, figure on losing a fair amount of velocity 50-8- fps) if your temperatures dip into the 50s. Win 231 doesn't like cold weather. If you know you're going to be chronoed early on a cold day, stick your ammo on the top of the dash board and turn the defrost on to High Heat... then keep the chrono loads in a pocket... next to your warm body, and run those. You might get as much as 80 fps between those and the cold loads in your range bag.
Chris Christian
Going to have to do some testing with Power Pistol and W231 at high and low temps now. And yet another project.... least this will be an easy one with my established loads.