Since our hero likes good hitting power & long range performance in a handy rifle, he might find the .375 Raptor cartridge in an AR-10 type weapon interesting. It has higher muzzle velocity & energy than either the .458 SOCOM or .50 Beowolf & the bullets have a higher ballistic coefficient for better long range performance. Also, since it uses the original .308 cartridge necked up, you can still have full magazine capacity.
http://www.375raptor.com/375RAPTOR/