Well said Grumulkin.
I'll add the question... why?
Having had four SSK 375JDJ's since the very early 80's, shooting an uncountable number of rounds with them hunting, LR hunting and just plinking with what was one of my favorite Contender cartridges, I can't see a valid need to push them any harder. Loads that approximate JD's 270 and 300 grain loads give very impressive results, even at long range out of a short barrel.