There were several delayed blowback carbine sized .30 carbine weapons designed after WW2. The French made a few, though I don't think they issued those, and the Dominican Republic built some on a design based on the Berreta SMG with a unusual delayed opening bolt feature.
In the Phillipines they have made advanced ignition short barreled machine pistols in .30 carbine. These being black market PDW type weapons sold to those civilians who feel vulnerable to guerilla or pirate attacks.
A short barreled .30 Carbine weapon looses a lot of muzzle energy.