I live in Las Vegas. Lately temps have been 105-110. I shoot in the AM when temps are only 100. I'm not using a strain gauge on my Ruger 416, but I have zero extraction problems, and no other obvious signs of overpressure. I had the rifle in Botswana and it went bang as advertised.

if I don't have heat-related problems in the gentle air of Las Vegas (like a convection oven), I don't expect any problems from my Hornady ammo anywhere else.