This is from the Ken Waters "Pet Loads" book. All loads are for 400gr bullets:60gr -IMR 3031/2182fps for a muzzle energy of 4228fp [accuracy load]to aMAX of 68gr of IMR3031-2400fps and 5112fp muzzle energy! 68gr IMR 4320/2355fps and 4924 fp of muzzle energy to a MAX of 72gr same powder giving2447fps at 5320fp of muzzle energy.[70gr of IMR 4320 was the best load giving 2400fps and 5116 fp muzzle energy!Win 748-66gr-70gr MAX and lastly IMR 4064 66gr-70gr MAX same bullet. I have data for 300gr bullets as well.Brass is easily made FL sizing .458 Win Mag brass........Have fun....Harold PS *use this data at own risk and start at the lowest charge first and go up from there. If you have a FAX # I can send you the complete write up?