It is a completely different firearm and it fires a different type of ammunition. Army began using the current naming system where the "M" is the designation for Model and the "number" represents the sequential development of equipment and weapons.
It was simply called a carbine because it is smaller and lighter than the Garand. Therefore, the "M1 rifle" was the first rifle developed under this system.
The second prototype competed successfully against all remaining carbine candidates in September 1941, and Winchester was notified of their success the very next month.
Standardization as the M1 Carbine was approved on October 22, 1941.
The "M1 carbine" was the first carbine developed under this system. Army Ordnance received reports that the full-size M1 rifle was too heavy and cumbersome for most support troops (staff, mortarmen, radiomen, etc.) to carry.
The "M2 carbine" was the second carbine developed under the system, etc. During prewar and early war field exercises, it was found that the M1 Garand impeded these soldier's mobility, as a slung rifle would frequently catch on brush, bang the helmet, or tilt over the eyes.
The first model was developed at Winchester in 13 days by William C.
Roemer, Fred Humeston and three other Winchester engineers under supervision of Edwin Pugsley, and was essentially Williams' last version of the .30-06 M2 scaled down to the .30 SL cartridge.
At 100 yards (91 m), the M1 carbine can deliver groups between 3 and 5 inches, sufficient for its intended purpose as a close-range defensive weapon.
The M1 carbine has a maximum range of 300 yards (270 m).
This patchwork prototype was cobbled together using the trigger housing and lockwork of a Winchester M1905 rifle and a modified Garand operating rod.
The prototype was an immediate hit with army observers.
.30 caliber semi-automatic carbine that was a standard firearm for the U. military during World War II, the Korean War and well into the Vietnam War.