Try googling .458 SOCOM forums, a website started and maintained by Marty Ter Weeme. This is the guy who conceptualized and designed the cartridge so it's the best resource I know of.
I use 35 grains of H-110 behind a 300 grain bullet; gets me 2,000 fps from a 16" Rock River. Shoots flat and hits hard at 100 yards, drops about six inches at two hundred yards and still hits hard. Don't forget this cartridge uses a large pistol primer, not a rifle primer.
I'm very fond of this cartridge; it's a great companion while walking and hunting in bear country. Your buddy will like it also I'm sure.
Last edited by Joatmon; 10/15/11.
