For all-round use I rely on my old Ruger in .416 Rigby with Zeiss 1,25-4x24 mounted on EAW QD-mounts. Shoots like a varmint rifle.
For really serious hunting in the thick stuff I would prefer a Heym 88B Safari in .500 N.E. with open sights.
As a third rifle for lesser game why not a falling block rifle, let's say a custom job based on a Browning 1885 High-Wall action, custom stock and barrel, caliber 8x75RS or .338-06 A-Square. Quality open sights from Recknagel (ERA) and a Zeiss 1,5-6x42 with EAW pivot-mounts, that would be my dream rifle for plains game !

Kalunga