My previous hunts to Africa have all been during the months of July and August. However, this year I will be hunting the first week in November. I expect the temp. to be around 100-110 degress. I will be taking my .500 NE and either my .458 Lott or .450 Dakota. Current velocity on my .500 is 2120, my Lott 2250 and the Dakota about 2275. These velocities were chonographed in 75-80 degree weather. Can you guys help me in regards to the increase in velocity in the warmer weather. I am quessing I will have to back off a few grains??
Thanks in advance

If you use powders that are not sensitive to heat such as Hodgdon's 'Extreme' powders, you should not have to worry about ambient air temperatures. That does not mean you should leave the ammunition sitting in direct sunlight or sitting on a hot engine block before firing them.

I used my .470 Capstick (500grs.@~2380fps) in 100+ degree temperatures in Tanzania with no obvious pressure signs.

George

Just from my past looks at temperature versus velocity in the .375 Weatherby and 404 Jeffery, my impression is:

Velocity increase per degree F temperature increase:

Varget, H4350, H4831: 0.5 fps/degree F
RL-15: 1.0 fps/degree F
IMR-4350: 2.0 fps/degree F

I think it is true that the Hodgdon Extreme line of powders is less temperature sensitive. Thanks to Australia, where those powders are made.

For the IMR family of powders expect a change of 3 feet per second for each degree of F change in temperature.
The Reloader and Hodgdon families of powders are less tempurature sensitive. Hodgdon Extreme powders are least sensitive.
Sincerely,

I'm not sure you can actually nail down a precise increase in vel. per deg. of temp, regardless of powder choice. I have found bore diameter & powder volumn vary so much between the diff carts, that som show higher variations than others. I have always experienced higfher vel. when the temps get into the mid 90s+ though, always.

The Winchester ball powders are temperature stable also. I think they have a lower burn temperature as well.
Take good care,
Dave

the best you can hope for, as there is so many variables, is to have a rule of thumb. Scientist used "STP" which is standard temp. pressure. That's 70deg at sea level, iirc.

hotter than that, at sea level, will go something faster, and colder, somewhat slower..

but, until you geting into pressure, not by an important margin for big bores..

don't even think about shooting your "max" load, from 50deg, at 120deg

jeffe