OP said "under-rated" not "under-rated 100 yrds cartridge".
@603Country... the triple deuce is a couple hundred foot pounds behind .223. Are you thinking .222mag?... which is pretty much the same as .223.
The .223's terminal ballistics are spectacular IMO. Not saying it's good at 1000 yards, but out to 400 or 500 modern projectiles have made that round shine.