I have been shooting .458 WM rifles for 30+ years... I love the bigger bores on bears and moose and have taken quite a few deer in the swamps with them too. A couple years ago I sold my Ruger No.1-H in .458 WM and kept my RSM in .458 Lott, then built a stainless Carbine in .458 WM for fast handling situations. I have loads from 350 - 500 grains with various powders, mostly H4198 on the low end and H335 on the high end and H4895 for reduced bear loads. I use filler with reduced loads although it is not strictly required, I feel it improves consistency shot to shot. If you like, I can PM my load notes on the understanding that you should safely work up your own loads for your rifle.
What rifle do you have, I did not see that noted?