Temperature impact on velocity/pressure?

[John Browning]

I finally got out to shoot my new G20 over a chronograph. I've completely fallen in love with the 10mm and the G20. Even with hotter loads, it is soft shooting. With it 100% stock, I have also had no issues with smiles, case bulge, frame battering, etc.

My goal is a 200gr bullet at the original Norma load velocity of 1200fps. A 200gr Nosler over 8.2grs of Longshot and a WLP gets me 1130fps. However, it was about 29 degrees when I was shooting. I don't want to run into issues when it gets hotter, but the cartridge shows no signs of pressure issues during my last trip. Is there any way to predict how much extra velocity and pressure I would get if it were a 100 degree day? Obviously I can test it when it gets hot, but is there a formula that gives a good estimate of velocity/pressure/temp relationships? Thanks.

[sargenv]

Specific powders are temperature sensitive.. others are reverse temp sensitive (the colder it gets, the higher the pressure). It's all confusing but if you want the lowdown on whethere your powder is like that or not, contact the manufacturer.. they've likely done the tests at all temperatures and can tell you one way or another.

Alliant Steel, a magnum shotshell powder was designed with a lack of temperature sensitivity in mind. It performs the same whether it is 90 or 20 degrees. Blue Dot, a very popular powder 25 years ago for waterfowl hunting, has issues when the temperature drops. Steel was a direct replacement for it.