Reloading especially for African temperatures?

[Rule 303]

I have used the same loading for temps at 115*F and -2*F. Never had a problem. I do not try to hunt at such temp extremes but it has happened.

What powders were you using?

Reason I ask is I use to use IMR 4350 for the 270. This was back in the 70's and early 80's. Loads that were good in winter, spring and autumn were hot in summer cause sticky extraction and extremely flat primers. I lived in Victoria, Australia then. Started using AR2209 no problems. No chrony back then so do not know the velocities. The primers when using 2209 were just starting to flatten so I would say it was near max load.

 

[GuttormG]

GuttormG, what powder were you using?

Norma MRP for the 7mm RM, factory ammo for the 308win (norwegian army surplus 7,62x51, all from the same lot).

 

[GuttormG]

I hsve been told by very informed sources that the powder used for the 7,62x51 is named NC1055, it is not available to us reloaders.

 

[Pondoro]

I fired a few shots from my old brit double in .475NE in Africa in about 35 degrees centigrade with (modern) Kynoch factory ammo. That ammo gave an average of 2158fps over the crono in 20 degrees C. That is pretty hot from 23 " barrels.

No pressure signs or altered impact in African temp.

Due to scope trouble on my .375H&H Brno 602, I fired 5 shots on an improved range in Botswana in 40 degrees C...after 3 shots fired the barrel was damn hot...after 4th and 5th shot fired the bolt started to stick, ie a sign of overpressure...needed some effort to open the action. The load was 80 grains Norma 160 behing a 300 grain Hippo homogenous brass solid.

 

[lcq]

If you carefully go over Hodgdons claims it becomes apparent that "temperature stability" is for falling temperatures. As others have noted, develop your load at the same or hotter temperature and you will be safe. You may lose a few fps but the animal won't know the difference. I used RL26 in my 7 mag and never had an issue. My load development was at the end of this winter (sub zero) but I kept the ammo in a cooler with a heat pack.

 

[Matt_WY]

This is a relatively recent article that I found interesting. It doesn't compare all powders, but definitely seems to give the nod to the Hodgdon extremes as the least temp sensitive. I doubt you will blow up your rifle with any modern powder, but if you are loading to try to maintain accuracy, then the variability they saw could make a difference -- especially if you test your loads in comfortable home temps.

https://precisionrifleblog.com/2016/06/19/powder-temp-stability-hodgdon-extreme-vs-imr-enduron/

Very short summary...
Difference in average velocity when going from 25 to 140 degrees:
h4350: 25 fps
varget: 46 fps
imr4166: 52 fps
imr4451 68 fps