You never hear about combat troops, the ones that actually fight, not just lay down fire in support, ever seeking out lighter calibers AFTER they have combat experience. Even commando types that normally like and need the lighter handier types.
Still, there is a need and niche for a small compact weapon, not a pistol, and not as big as a rifle, that shoots an effective round.
THIS guy has done a lot of thought that parallels my own for carbine selection.
I like his thought process, but it doesn't match mine completely. He'd be happy enough with a tiny round like the FN 5.7 mm type used in their P-90. Kinda, but different.
It violated some of my requirements. I want a carbine that shoots a common cheapish, but effective, pistol caliber out of a longer barrel. Preferrable the same caliber that I already own. A new expensive bullet would not make me happy. And I obviously need a civilian legal version. No select fire.
If the M1 Carbine had come in .45 instead of it's own caliber I'd be as happy as a pig in poop. Reliable, handy, perfect. And perfectly non-existant.