Heat is an over rated issue IMHO.

I have loaded in Winter (5 - 20 degrees) and then
got on a plane and landed and hunted in 30 - 45 degrees
if not more. Ammo is belt has been damn hot but it all
worked 100% OK in both Bolt's and Doubles.

And some of the loads were "HOT" loads where I was
testing bullets at a velocity as fast as we could
push them - out of 375H&H, 9.3 x 64 etc.

Unless others chamber the guns in those calibres,
it will be hard for them to pass muster.