With a senseable powder charge the 450, to 480 gr bullets are perfect for the 458 Win Mag. The 458 Win Mag cannot be made to do what the factory said it would do, but it is a good cartridge none-the-less, "IF" you use a lighter bullet, like the excellent Woodliegh 480 gr soft, and solid, or as 475Guy suggested a North Fork soft, and now the soon to be avalible, solid by them as well. However, it will not handle the 500 gr bullet properly,without crushing the powder and building too much chamber pressure, and certainly not the 600 gr bullet,under any cercumstances. The 600 may get out of the barrel, but it will not be setting any speed records, for sure. The other thing that happens with crush loads is, after some time the powder becomes a solid, and you get hang fires, squib loads, or complete missfires. Those are the things that got people in trouble when shooting large fight back animals with the early factory ammo, and destroyed the reputation of the 458 Win Mag. It will never be a 450NE, or 470NE, but it can be used, if handled properly, with great success!