Greater backthrust do to the less parallel shell case to chamber wall bearing surface. (not as much grip)

Also coincidentally why the HH design extracts 100% reliable even in horrible conditions and with high heat.

I think the Lower pressure has to do with the greater case volume? What is the difference in case volume? Does the blown out 338 case have a close capacity to the HH case?

I use RL15 with the 270 grain bullets. I have loaded to 77 grains where I saw pressure issues. Those bullets left the barrel in the mid to upper 2800 range.

With 76 grains I never have pressure problems and the velocity was about the same. With 75 grains it's absolutley no problem and the velocity is just over 2800 fps at 60-70DegF
This leaves me margin for error in South Africa for the higher temps. My loads are now and have always been used with 210's not magnum primers. When I used Magnum primers my accuracy was a bit inconsistant. With the large rifle Primers they shoot like a target rifle! I also crimp them fairly tight with a Lee factory crimp die. I can have no risk a bullet comes lose from the shell!

I have shot a few Hornady Heavy Magnum factory loads with the 270 grain bullets. They were 2850fps dead on the money and shot into the same clump of holes in the target as my handloads do. They also used 76 grains of powder( I took one apart)

I suspect I could fit 80 grains of powder or a bit more into this case. What is the capacity of the 338/375 case?

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