Scopes back in the day flat out sucked compared to modern standards. Shots beyond 1000 meters were pretty much impossible considering the technology. If you can slap a simple 2.2-4X scope to a rifle which weighs 40 pounds that fires a bullet that one won't even be able to observe outside traditional effective range of the infantry rifle's round with a weak, albeit state of the art optic, next to something less than a quarter of the weight, firing the same bullet as the standard infantry rifle, with an effective range well within view or practicality, most will take the latter.

Didn't have the accuracy, for one. I own a PTRD-41, and it is in no way capable of the accuracy required for shots over 300M. They're designed for (relatively) close-range penetration, not range.

I always thought that the supposedly "on the drawing boards but never quite took off" external magazine fed M-1 Garand in .276 Pedersen would have been great.

Further more, I once read a short story in Military History Quarterly about Marine Raiders and the 1st-SSF, the "Devil's Brigade" carrying both Government Models in .38 Super and Smith and Wesson Heavy Duty revovlers in .38/44

existing technology

Maybe a double stack 1911

That WAS existing technology. M8 Greyhound armored car mated with a Maxon mount.

Although, I'd think the existing Maxon/M3 Halftrack combo was much more mobile.

Seeing as how the U.S. military was already supplying .38 Spl, .45 ACP, .30-06, .30 Caliber Carbine, and .50 BMG to all fronts, why not replace the .30 Caliber Carbine with a .270 in the same platform.

That would have been one hell of a weapon.

It would have been cool if one of the higher up commanders or Generals carried one of those full-auto converted 1911 pistols that John Dillinger and Baby Face Nelson used.

Aside from making them look like a total badass, I imagine such a weapon would be intimidating to the enemy.

True, but I can't see that being practical in a .45 ACP weapon.

Dillinger's were .38 Super if I recall correctly.