The M1
Garand was the weapon of choice for infantry.
The M1 Carbine, half the weight and with a less
powerful cartridge, was the weapon of choice for
support troops, and others not primarily involved
in infantry combat. It was designed to meet
combat needs less demanding than the M1 Rifle,
but more than can be met by the M1911A1 pistol. It was more
convenient to use than the M1, and less intrusive
to their other duties, while still much more
effective than hand guns.
Originally, the M1 was to be
capable of selective fire control, but this was
dropped. Because a demand arose for an automatic
capability, the M2 was
developed, with a selective-fire switch added to
the left side of the receiver, operating on the
sear mechanism.
The US Carbine, Caliber .30in,
M3, or T3, was simply an
M2 with suitable mountings prepared on the
receiver to take various models of infra-red
night-sighting devices. No open or conventional
sights were provided, and the IR carbine mounted
an M3 flash hider, a simpler design than that for
the M1C Garand. The M3 carbine, (its development
title was T3), was produced in limited numbers as
a semi-prototype. Only about 2100 were
manufactured compared to 5,510,000 M1 carbines,
150,000 M1A1 carbines and 570,000 M2
carbines.
The M1 and M2 Carbines were also
much more powerful than the Russian type burp guns used
by the North Koreans and, later, the Chinese,
having more than twice their muzzle energy.
In the infantry, the M2 Carbine
was carried by Staff NCOs and officers. With its
30 round magazine, rapid fire and greater
stopping power, it was an effective counter to
the various submachine guns used by the
Communists in the Korean War.
In intense cold, however, such as
the Chosin battle, light weapons such as the
carbine and air-cooled .30 calibre light machine guns malfunctioned
much more often than the M1 and the water-cooled heavies, with
anti-freeze in their jackets. The Marines used
alcohol based hair tonic as anti-freeze
lubricants for all light weapons, with good
success, but the carbine components were small
and fragile, and repeatedly malfunctioned.
The Carbine continued to be used
in Viet Nam, until replaced by the M16.

The following additional
information is courtesy of:
R. E.
Sullivan, Colonel, USMC ('43/'67)
(Ret.), Sun, 28 Nov 1999
The most unattractive feature of
the M-1 Carbine as we had them in WW II and up
through at least part of 1948 was the leaf type
sight. There was no windage adjustment at all,
and I've fired record on the range with those
things, on say target 20, but had to hold in the
left side of the bull on target 18. Then in
'48 we got a modification that put a ramp
type sight for elevation and an actual movable
peep for lateral movement. Now those were worth
taking to the dance. One thing about bullets,
impact, weight, muzzle velocity etc. that
afficionados of weapons take so seriously: My
experience, on many battlefields, is that if you
get a head shot or a pentrating wound to the body
cavity, it takes the spirit of the bayonet plumb
out of the individual you're shooting at.