There is no reason the new catridge has to be loaded hotter than the H&H , if you think about it the 300 Win has quite a little more speed potential than a 300 H&H(larger powder capacity) so with prudent loads , extraction under very hot conditions should be a non-issue .
As to the neck length , that should also be a non-issue , the old H&H doesn't have all that much neck to start with . Bump the 300 Win case up to 375 and you will have a neck length very close to the H&H .
As to reliabilty under poor condtions , I see no reason a this new cartridge will be any different than any garden variety 338 or other belted case..........
I'm sure though , the fellas that get to Africa alot will stick with their H&H rifles , if nothing else , there will always be a big concern for ammo re-supply , but some of us home bound characters that like to play with big bores and occationally make a stab at collecting an elk or moose may buy the new round......
