M-1 Carbine, why not .45 Caliber?

[PurpleAngel]

When the U.S. Military (1940?) came up with the M-1 Carbine for non-front line troops, why could they have not just have used the .45 round instead of the .30 carbine round?

[banger]

First, allow me to confess....

I am pulling this from my butt....

However, I seem to recall that the original spec. called for an effective range of 200 yards.

This alone would have disqualified the .45 from possible adoption.

[collim1]

They needed more velocity in order to have a 100+ yds effective range.