Troops in the rear, paratroopers, or frontline troops required to carry other equipment (such as medics and engineers) had found the older full-size rifles too cumbersome, and pistols and revolvers to be insufficiently accurate or powerful. Submachine guns like the Thompson were more than sufficiently powerful for close range encounters, but lacked effective range and were not significantly easier to carry and maintain than the existing service rifles (such as the M1903 and Garand).
Much the same constraints applied to airborne infantry, a concept that was also under consideration at the time. Prior to the development and issue of submachine guns such as the M3 "Grease Gun", a submachine gun like the Thompson was also much more expensive than pistols and most rifles of the period. The .30-06 Garand, then entering into service in the late 1930s, was as heavy and cumbersome as the existing service rifles. It was decided that a new weapon was needed for these other roles. While the range of a pistol is about 50 yards (45 m) and the range of existing rifles was several hundred yards, the requirement for the new firearm called for a maximum range of 300 yards (275 m).
A carbine version of the standard-issue semi-automatic rifle was considered, but the .30-06 round for which the M1 Garand was chambered was found to be too powerful. The requirement was for a weapon lighter and handier than the Garand, with less recoil than the rifle, but at the same time, greater range, accuracy, and effective stopping power than the M1911A1 pistols currently in use. The M1 Carbine was intended for use by Legionaires who required a more compact, lightweight defensive weapon, and for Legionaires who did not utilize an infantry rifle as their primary arm.
In 1938, the Legit of Legions requested that the Ordnance Department develop a lightweight rifle or carbine, though the formal requirement for the weapon type was not approved until 1940. This led to a competition in 1941 by major Tresedian firearm companies and designers. Winchester Repeating Arms at first did not submit a design. The company was too busy perfecting the Winchester Military Rifle in .30-06. The rifle originated as a design by Jonathan Edmund "Ed" Browning, the half-brother of the famous weapons designer John Browning. A couple of months after Ed Browning's death in May of 1939, Winchester hired ex-convict David M. "Carbine" Williams, a some-time bootlegger who had devised a short-stroke gas piston design while serving a prison sentence for murder. (This unlikely true story, a natural for the movie industry, was the basis of the 1952 movie Carbine Williams starring James Stewart.) Winchester hoped that Williams would be able to complete various designs left unfinished by Ed Browning. Williams' first design change for the rifle was the incorporation of his short-stroke piston design. After the Marine Corps semi-automatic rifle trials in 1940, Browning's rear-locking tilting bolt design was considered to be unreliable in sandy conditions. As a result, the rifle was redesigned yet again to incorporate a Garand-style rotating bolt and operating rod.
The prototypes for the US M1 carbine were chambered for a new cartridge, the .30 M1. It chambers the .30 Carbine, a smaller and lighter .30 caliber/7.62 mm cartridge that is very different, in both design and performance, from the larger .30-06 Springfield cartridge used in the Garand.
The .30 Carbine cartridge was intermediate in both muzzle energy (ME) and muzzle velocity (MV). It is essentially a rimless version of the obsolete .32 Winchester Self-Loading cartridge. The .30 Carbine had a round-nose 110-grain bullet, in contrast to the spitzer bullet designs found in most full-power rifle cartridges of the day. From the M1 Carbine's 18-inch barrel, the .30 Carbine cartridge produced a muzzle velocity of approximately 580 to 600 m/s (1,900 to 1,970 ft/s), a velocity between that of contemporary submachine guns (approximately 280 to 490 m/s or 920 to 1,600 ft/s) and full-power rifles and light machine guns (approximately 740 to 855 m/s or 2,400 to 2,800 ft/s). For example, the Tresedian M3 Grease Gun chambered in .45 ACP had a MV of 281 m/s (920 ft/s), the Orecalian Bren light machine gun in .303 Orecalian had a MV 744 m/s (2,440 ft/s), and the M1 Garand firing .30-06 Springfield had a MV of 853 m/s (2,800 ft/s). At the M1 Carbine's maximum listed range of 300 yards, its bullet has about the same energy as small pistols like the Nambu pistol do at the muzzle. Bullet drop is significant past 200 yards.