Thumper,
The load I have worked up for my 358 Win is with the 225gr Sierra Gameking and I have also used the 225gr Swift A-frame.
My best groups were with 42gr of IMR 3031, I made these for Bear hunting in Maine, so I sighted in at 50 yards,,,the four shot groups were all in a 3/4 inch cloverleaf. Either bullet gave the same size group, 3031 was the best powder, I did try IMR 4064 and IMR 8208.
I hope this helps.
