|Designer||Frederick L. Humeston|
William C. Roemer
David Marshall Williams
- "Keep firing on that window!"
- ―Miles to the American Soldiers
In selective-fire versions capable of fully automatic firing, the carbine is designated the M2 carbine. The M3 carbine was an M2 with an active infrared scope system. Unlike conventional carbines, which are generally shorter-barreled versions of a longer parent rifle (like the earlier .30-40 U.S. Krag rifle and carbine and the later M16 rifle and M4 carbine), the M1 carbine has only one minor part in common with the unrelated larger M1 Garand, a short buttplate screw, and fires a different cartridge.
Sergeant Miles carried an M1 Carbine.
The M1 carbine's bolt mechanism is similar to that of the M1 rifle, though the carbine has a different gas system and trigger mechanism design. The gas system is a lightweight tappet-and-slide gas system. Initially fed from a 15-round magazine, a 30-round magazine was introduced for the M2. The very first carbines, those made before mid-1943, were originally equipped with an extractor with a "V-cut" plunger for removal of the fired cartridge case from the chamber. The "V-cut" design was found to be flawed and unreliable. In the field "V-cut" extractor plungers were reground to a straight configuration, which enhanced reliability, until factory production was able to supply the better design. 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 gr (7.1 g) bullet, in contrast to the spitzer bullet designs found in most full-power rifle cartridges of the day. From the M1 carbine's 18 in (460 mm) barrel, the .30 Carbine cartridge produced a muzzle velocity of approximately 1,970 ft/s (600 m/s), a velocity between that of contemporary submachine guns (approximately 900 to 1,600 ft/s (300–500 m/s)) and full-power rifles and light machine guns (approximately 2,400 to 2,800 ft/s (700–900 m/s)). At the M1 carbine's maximum effective combat range of 300 yards (270 m), its bullet has about the same energy as pistol rounds such as the 8mm Nambu at the muzzle. Bullet drop is significant past 200 yards (180 m). One characteristic of .30 Carbine ammunition is that from the beginning of production, non-corrosive primers were specified. This was the first major use of this type of primer in a military firearm. Because the rifle had a closed gas system, not normally disassembled, corrosive primers would have led to a rapid deterioration of the gas system. The use of non-corrosive primers was a novelty in service ammunition at this time. Some failures to fire were reported in early lots of .30 Carbine ammunition, attributed to moisture ingress of the non-corrosive primer compound.
Categorizing the M1 carbine series has been the subject of much debate. The M1 is sufficiently accurate at short ranges. At 100 yards (91 m), it can deliver groups of between 3 and 5 minutes of angle, sufficient for its intended purpose as a close-range defensive weapon. Its muzzle energy and range are beyond those of any submachine gun of the period, though its bullet is much lighter in weight and smaller in diameter than that of .45 caliber weapons, and much less powerful than those of other service rifles of the period. The M1 and later M2 carbines were never designed to be assault rifles, such as the later German StG 44 and Russian AK-47, and the .30 Carbine cartridge gives up significant muzzle velocity (roughly 350 ft/s (110 m/s)) to both. Additionally, the bullets used in the cartridges of the AK-47 and StG44 are spitzer designs, and suffer less energy loss and trajectory drop at distances beyond 100 yards (91 m). Most authorities list the effective combat range of the M1 carbine at around 200 yards (180 m), compared to 250-300 yards (230–270 m) for the AK-47 and StG44. The M1 carbine entered service with a standard 15-round magazine. The introduction of the select-fire M2 carbine in October 1944 also brought into service the 30-round magazine or "Banana Clip". Perhaps the most common accessory used on the M1 Carbine was a standard magazine belt pouch that was mounted to the right side of the stock and held two extra 15-round magazines. After the introduction of the 30-round magazine, it was common for the troops to tape two 30-round magazines together. This led the military to introduce the "Holder, Magazine T3-A1" also called the "Jungle Clip", which was a metal clamp that would hold two magazines together without the need for tape. Due to requests from the field, the carbine was modified to incorporate a bayonet lug starting in 1945. However, very few carbines with bayonet lugs reached the front lines before the end of World War II. A folding stock version of the Carbine (the M1A1) was also developed after a request was made in small numbers for a compact and light infantry arm for airborne troops. After World War II, the M1 carbine became a popular plinking and ranch rifle. It is still popular with civilian shooters around the world and is prized as a historically significant collector's item. The Carbine continues to be used in military marksmanship training and competitive target matches conducted by rifle clubs affiliated with the Civilian Marksmanship Program (CMP.)