The M1 Carbine is the standard by which all PDWs are measured.

[VASCAR2]

I assumed the 30 carbine round nose bullet was used to improve feed reliability with a short cartridge case and detachable box magazine. I always thought of the 30 carbine more of pistol caliber ballistics and not rifle ballistics. The 357 Magnum, Remington 38-40 or 32-20 from lever guns class of cartridge.