It's human nature i suppose - we'll forever wonder, 'what if' and try to squeeze more potential out of our rounds.
I have no doubt that each and every calibre i have and presently own is more capable than i, yet i am forever tempted by another.
i've have owned 6mmBR, 6.5x55 swiss, 6.5 grendel (straight pull rifle) and am currently experimenting with 7.5x55 (straight pull again) and considering 6.8mm SPC.