Well kinda... all the original Winchester 'short mags' (.458, .338, .264) started life as ye olde .375 H&H, cut down to fit in a standard length action. The .458 was the first to be released, so yes it was the 'father' of the .338 and the .264, but really all three are children of the .375... semantics;-)
The .458 is dead ###y, no doubt about it, but you NEED to reload it. Luckily it's also an easy cartridge to reload, and you can work your way from full-bore elephant medicine all the way down to soft elk/moose loads. I used to shoot one that duplicated a very hot .45-70 Ruger #1-only load, using a 425 grain hard cast. Wasn't exactly pleasant to shoot, but at least I didn't need my chiropractor on speed dial...
I found that the old Barnes X bullets were very accurate in mine, if you can find any it might be worth playing around. Though it's probably much easier (and just as accurate) to work up some loads with the new TSX.