It this something we in the south really need to be concerned with? I use Ramshot TAC in my 308, CFE223 in the Whelen, IMR 4350 is what I’m gonna test next in the 243s, H335 in the 7.62x39 and Grendel, BL-C2 in my 223. None of the are temp stable. My main concern is TAC, CFE223, and IMR 4350 as these are rifles are used regularly during the seasons. Am I over thinking this or should I be concerned?

The short answer is YES.

No powder is stabile from 0 - 100 degrees, even the powders listed as temperature stabile. But some powders definitely see bigger changes in velocity / pressure as the temperature changes.

TAC will be more temperature stable than H 335 and BL-C2.

If your going to use these guns when temperatures are north of 75`, stay short of maximum loads. In hot temps, pay attention to the case for hard extraction and flattened primers.

Thanks!! My loads are below max on everything. I’ve shot everyone of the different loads in 90+ degree weather and had no issues as far as pressures go. I should be ok with “normal” hunting temps? When I purchased a lot of the powder I have, I didn’t realize that temperature would play a factor in loads. I do have some H4350 on the way and use Varget in the 7-08. Ive been educating myself on which Powders are stable.

Shoot your gun when the temps cool off and confirm zero. That's about all you have to do. I do most of my load development this time of year and in the spring... never in the heat of the summer OR dead of winter. It doesn't get cold enough here to usualy make a huge difference but I have seen it and experienced it. Just shoot a 5 shot group and confirm.

Thanks!! Tomorrow morning will be the perfect weather I think. Supposed to be in the 50s here.

I saw some data on tests with ammo chilled to specific temps somewhere in the past... I cant remember the specifics, but this guy stairstepped cartridge temps using temp stable and unstable powders from freezing up to something along the lines of room temp. There was a velocity response to the predisposed chilling for both types of powders, but I remember thinking that it wasn't as bad as what I imagined it would be, even with the temp unstable powders.

That probably doesn't help you much, but much like Goatkiller suggested, as long as you aren't developing your loads in late July and August and not verifying the loads before hunting in January, it's probably not going to make a significant difference.

As always though, it doesn't hurt to verify anything by some careful practice. Who doesn't like to shoot their own ammo anyway??

I've got different loads for different temps but usually it's not gonna be that big of a deal in a hunting rifle.

Usually not an issue but if you do load development when it 45° and go west to Texas you may be hunting in 80-90° weather it can be an issue with max loads using temperature sensitive powders.

Another issue is lot to lot variations with powders. R22 is a great Magnum rifle powder but notorious for temperature sensitivity and lot variations. I almost locked up the action on my 300 Weatherby a few years ago because of this. It was a little warm that day and I had just loaded 20 rounds with a new bottle of R22. My load was 86 gr under a 168 gr TTSX for 3300 fps. When I tried to open the bolt after the first shot it wouldn't budge. Looked at my chronograph and the velocity was 3460 FPS! I finally got the bolt open with some effort. Pulled all of those bullets and had to redevelop the load. Ended up with 83 gr of powder and 3300 FPS.