RE: .243 vs .257 vs .277 vs .284 vs .308 vs .338 vs .458
30-30, bolt-action?
I never heard of those, but they do make swell lever-actions.
What in the freaking heck is a .284? Are you talking about the 7mm Rem Mag?
IMO, the 7mm Rem Mag would be a good choice in the Browning BAR Safari.
I like the .308 myself, though, and it shoots swell!