I helped a coworker buy a RA 458 upper. Sounds identical to the one you have. He had zero reliability with gun show purchased ammo ("newly manufactured"), but 100% reliability with known name ammo. He was impressed with the cartridge's performance against wood (dead trees at 10 yards). His testing showed a lot of bullet drop over 100 yards. I think he ended up zero'g at 75 yards.
He bought it for hog hunting.
I'd view a 458 SOCOM upper as I would any other specialized HUNTING gun. Personally I don't hunt so I don't have any dedicated hunting guns. I don't see any other reason to own a 458 SOCOM.
Your 300BO negates the need for the 458.
EDITED: I'm not a wildcat person since I don't reload. I want to have common ammo availability. As such, I think there are better defensive options than the 458. 12 gauge, 5.56 and 7.62x51.
Last edited by Architect; 03/29/16 08:57 AM.