Red Dot, Blue Dot and Green Dot are all very temperature sensitive! Hodgdon "Extreme" powders are suppose to be LESS sensitive, but +100 degree temps will affect loads developed below 65 degrees, and vise versa. But 5 grains of 231 always burns the same at 70 degrees weather loaded at 45 or 95 degrees, same for all dry propellants. (The military liquid artillery propellants are a little bit different! I think weight remains the same but the volume is adjusted.) When I developed my 223 Remington load back in the mid 80's, I used small rifle mag primers in hot weather. The longer duration 'flash' helps with cold weather ignition, but the load is still in safe pressures in hot temperatures. I've fired them on 105 degree days with the ammo laying in the sun without any primer cratering. On the other hand my recently developed 338 Lapua Mag load was around Max at 65-70 degrees (and it shot very well at 20 degrees), but on a 95 degree day the cases seized to the chamber! That is a Hodgdon US 869 load with a 300 grain bullet. I need to make a Retumbo or H 1000 load OR stick with the less desirable 250 grain bullet for summer use. One of my friends, loads high pressure Bench Rest loads, based on barometric pressure, not temperature. Shooting at 800' in Ohio is a lot different than 7000' in Montana! Ivan
