Our special forces actually used a modernized version of .45-70 in a specially chambered M-4 system for close quarters entry applications and blowing doors off their hinges.
They call it the Alexander Arms Beowulf .50
They loved it when it worked but it was unreliable in full auto in the M-4 so they moved on.
You kidding me? A 50 cal combat rifle? Did I hear you right?
I hadn’t thought of that. There is a role for heavy slugs. Full auto probably isn’t it unless in a bottleneck case.
I carried just about everything in my time but the M14 was the one I stuck with the longest. Loved that damned thing.