Try 122 to 133 grains of IMR4350 with 600 grain pills.

Try 128 to 140 grains of IMR4350 with 525 grain pills.

Somewhere with those ranges you will find the "sweet" spot.

Personally I liked to keep the 600 grain pills in the 2200 to 2300 fps range and limited the 525 grain bullets to no more than 2400 fps. They can be driven FAR faster though, but you shoulder may not appreciate it, and soft points will start to fail when striking bone.

It kills better than a 458, by the way.

Scott