A: .223 is just too small!
B: Are you saying US Army should have just kept the 45-70?
A: That’s an idea…but make it work in a semi-auto.
For people who prefer throwing 300-350 grains of lead with every trigger pull: Teppo Jutsu in .458 SOCOM. Take any .223 AR lower, swap the upper. Standard AR15 magazines work but hold 1/3 as much ammunition. OK, so there’s no free lunch. But .458 SOCOM (comparable to full power 45-70 in performance) would impress a bear whereas .223 might not.