There's not a "temp insensitive" powder made that not going to show at least 50fps between 5-90F. In fact I'd be happy with 75F.
Where the temp insensitive powders like the extreme line from Hodgdon benefit is going from 70-110F. They reign in the pressures in high heat. Cold weather not so much stability because it's not the concern.
Well……that's not entirely true either!
I don't know whether it was chronograph inaccuracy, cartridge case design, or load density (in this case a heavily compressed charge)…..but, I actually got a slight increase in average velocity when testing loads @ -3 F to zero vrs my load development temperature of 90+F.
This test came about, from a conversation such as this……so I was curious.
I use RL 17, stated to be very temperature sensitive, in my hunting loads. I do all of my load development @ 90+ F, allowing rifle and cartridges to reach ambient temperature…..as I load to maximum pressures and don't want unwanted surprises on a hot day.
I used the same procedure when shooting on the cold day. I left the rifle and cartridges outside for a couple of hours to achieve ambient temperature. I shot a 3 shot group @ 300, allowing a while between shots so that the heating of the barrel would/should not affect the velocities.
I actually showed a velocity "increase" of a few fps, the 300 yard group was as good as my warm weather groups and right where the shots were supposed to land!
Not at all what I expected……but, I'm pretty happy with the test results. An anomaly, very possible…..but, those were my findings on that morning! memtb
