Right quick – you’re dead nuts right about the 30 Carbine not being bottlenecked. See, officers during WWII only had pistols, since it was considered Tres Gauche for an officer to sully himself by carrying a Garand. So, the higher ups decided the officers needed something “better” to defend themselves with and came up with the M1 Carbine.
Now, the M1 Carbine ain’t a bad design. If it was chambered in anything other than the 30 carbine, it’s not a half bad little gun. But, the higher ups had 30-caliber-itis, meaning everything bigger than a 1911 had to be 30 caliber… because, by gawd, a rifle not being 30 caliber was just un-A’murkin!
So, they came up with that crappy 30 carbine round. I suppose if you were shooting someone next to you in a phone booth, it would be just fine… but when the bad guy scoots back a hundred yards or so… Boink! It just sorta bounced off the Chinese… not good.
The Russians always had their issues when it came to weapons design… like the PPSH? Not a bad design, but the Finns took it, improved it, made a shyte-pot of them, turned around and whupped the Russians with their own stuff… heh, heh… Called it the KP-31 and it has a cyclic rate of almost 1000 rpm… they mowed the Russians down like grass…
The wicked flee when none pursueth..." - Proverbs 28:1