Reinventing

[stickmaker]

There's a lot of talk these days - and nearly as much associated work - about the Pistol Caliber Carbine (PCC)  and the Personal Defense Weapon (PDW). These are often desired for government security or private body guards. The first is usually a short, semi-auto or full-auto rifle, something which can be used against targets beyond pistol range but which is handier than an assault rifle. The later is smaller - a submachine gun or even a large automatic pistol. However, both concepts involve a cartridge with lower power than even assault rifle ammo possesses, though something still effective at close range, in a compact firearm which feeds from a detachable box magazine and can fire rapidly. 

Isn't that pretty much a description of the M1 Carbine?

The .30 carbine cartridge is far from as potent as the .30-'06 or the 7.62 NATO or even the 5.56 or .30 Kalashnikov. However, it has a bit more muzzle energy than a .357 cartridge with a bullet of the same weight fired from a barrel of the same length. I don't think anyone would volunteer to be hit with either of those. 

The M1 Carbine is small for a rifle, but it is a rifle. It is capable of reliably hitting a man-sized target at over 100 meters, yet handy enough to be used at very short ranges. Cartridge and rifle were originally designed for a FMJ bullet, which greatly limited the effectiveness, but the combo was still considered more than adequate for close combat. With modern JHP bullets it is far more effective. Moreover, the M2 Carbine was selective fire and came with a larger (30 rounds vs. 15) magazine.

So, the original M1 or M2 (or, more likely, an improved version, with a more reliable action and polymer furniture) could easily be adapted as a PCC. Put a removable butt stock on it and perhaps shorten the barrel a bit (there are pistols which shoot the .30 Carbine cartridge, but they are infamous for their muzzle blast) and you have a PDW which could be concealed under a suit jacket. 

No need to reinvent the wheel. Just slightly modify a known, reliable design. Which happens to be more than 80 years old. :-)