So working up a load and checking ballistics to coincide with turret for elevation. And I was wondering what kind of velocity loss due to the powder ignition (not air density etc.) I might be looking at so that I can adjust my load.

In other words, if I am getting 2750 fps at 80 degrees one day, how much velocity should I expect to loose when the temp dips to 60, or 20. Is it a linear relationship, or is there a range where there is little effect, and then it increases, as some posts I have read have suggested?

Unfortunately, living in Texas, my opportunities for testing cold temperature performance are fairly slim.

Thanks!

I have no way of measureing that, and don't know anyone handy that does..

I have, for test purposes, left my loaded rifle on the hood of a vehicle in the Big Bend country near Presidio, Texas where I ranched for many years and was raised, and no place in the world can beat that area with its 120 plus degress in the shade..then shot a magazine full with no noticeable results with RL-15, Rl-19, H4831 and IMR-4064 and a couple of others that I can't remember...I used a 30-06, 375, 338 win, 404 Jefferys and 416 Rem.

I have used a max or near max load of RL-15 in my .375 H&H with 300 gr. bullets at about 2550 FPS, the 30-06, 9.3x62, and 338 win., in Idahos hard winter months with temps below zero, and Tanzania, Zim and So. Africa when it was mighty hot and with satisfactory results. I have hunted in South West Texas and Northern Mexico using RL-15 in several different calibers with no problems..come to think of it I have used most US powders over there and never had these issues with any of it, contrary to what I have read so many times..Also observed many of the hunters I have sent over the world, and don't recall this issue ever coming up..

I'm pretty well convienced the real culprit is overloading not weather conditions. It is probably embarassing when this happens and who wants take the rap of poor handloading practices...DG calibers should never be loaded to max IMO. Function is more important than foot pounds.

No need to load beyond your rifles maximum in any hunting load, better to load it a grain or two under max, if you need more punch, get a bigger gun and load it a gr. or two under max.

What Ray said. Work up a good load that is accurate and not pushing pressure limits and faggetaboutit.
While it may be possible for trouble if you work up a MAX load at freezing temps then take your gun to the desert, if it works in Texas temps and you are going where it is zero, the loss of a few fps is the least of your worries.

Gentlemen,

Thank you for the responses. The load I am working towards is way below max from Nosler's manual, so high pressure should not be a problem. I was thinking of adding a little on top of my target to make up for the fact that the conditions I will be Chronoing in will be warmer than when I hunt. The reason is I read suggestions that a lot of velocity is lost, but it sounds like that's maybe a little over stated.

Thanks for the advice!

For buffalo and elephant I strongly suggest that you load the 375 H&h down to around 2500 FPS as that is where 375 bullets perform their best, Most PHs will agree with this and many elephant hunters say 2400 FPS is much better for elephant as the bullet yaw comes to rest quicker and yaw at close range is detrimental to penetration...

Also you did not mention what bullet weight you were useing and I'm talking about 300 gr. bullets..If your shooting 250 gr. bullets then 2750 is still just a tad warm IMO and perhaps cause extraction problem in very high temps if the gun was rested on the hot hood of a truck or whatever..I suggest 2650 FPS and you'll never know the difference in its effect on game.

Just keep in mind that it takes max or better loads to get you in trouble with temps. I have always loaded about two grains below max on most hunting loads in any rifle for hot weather, just to be not so much safe but to not have to deal with stuck cases etc. I have yet to have a problem with any caliber because of temps.

Chad,
Regarding loading the 375H&H down, let me tell you about my first safari. Like you I was very excited and reading everything I could find on loads. Kevin (Doktari) Robinson recommended the 375 be loaded down to 2400fps and that is what I did. The problem was that the bullets I used were soft (300gr Speer African Grand Slams) built similar to a Nosler Partition in that they have a front nose that expands rapidly, then a tougher shank. Before anyone flames me for disparaging NP, I only said the AGS's are built similarly, the Speers (at least 10 years ago) were too soft in the front. My PH told me to bring only softs as he would back me up with solids if necessary.
The problem I encountered is that the soft bullets expanded rapidly and coupled with the reduced velocity, gave poor penetration. This is not a good situation on buffalo and to a lesser extent, eland.
My take is that the reduced velocity advice should only be taken with tough, premium quality controlled expansion bullets or solids.
My last 2 buffalo were taken with Woodleigh 350gr PP at 2400fps and the results were far better.
Bottom line (for me) is load 300gr to no less than 2500.

I don't know if you can use this but I tested my 470 loads before going to Africa in 2009. I was loading 87gr of RL15 with 500gr Woodleighs (Kynoch wads). At 25-30 degrees my velocity was 2060-2080, at 70 degrees it was 2140-2150 and at 90+ degrees it was 2200. I was concerned about my regulation at lower temperatures but it regulated just fine from 2060 and up.