Personal defense weapon
Compact automatic firearm for secondary defensive use by support personnel.
A personal defense weapon (PDW) is a compact, magazine-fed automatic firearm, typically functioning as a submachine gun intended for backup self-defense rather than as a soldier's main arm. Some PDWs use a small-caliber (under 8 mm or 0.31 inches in bullet diameter), high-velocity bottleneck cartridge that is essentially a scaled-down intermediate round, placing them as a hybrid between a submachine gun and a short assault rifle. The term describes their original purpose: a small but potent firearm that support troops—such as military engineers, logistics drivers, medics, artillery crews, and signalers—could easily carry for personal protection. These "second-line" personnel are not front-line combatants but might face well-armored enemy skirmishers or infiltrators in close quarters, requiring a weapon with more range than a handgun but less bulk than a full-sized service rifle. Despite this concept, the PDW has generally not succeeded in its intended role, with carbines remaining the preferred choice for such duties.
**History**
In the late 1800s and early 1900s, shortened infantry rifles called "carbines" were issued to cavalry and gun crews. This practice faded as standard infantry rifles became shorter, like the Short Magazine Lee–Enfield. Handguns then became the typical self-defense sidearm, but they proved ineffective in most close combat. During World War I, the Mauser C96 and artillery Luger pistols were issued with attachable shoulder-stock holsters to improve control and accuracy.
Also during WWI, the United States secretly developed the Pedersen device for the M1903 Springfield rifle. This attachment let the rifle fire the .30-18 Auto (7.65×20mm Longue) pistol cartridge in semi-automatic mode, allowing a soldier to convert his rifle into a form of submachine gun or automatic rifle in about 15 seconds. Production of the device and modified M1903 rifles began in 1918, but the war ended before they could be sent to Europe. The contract was canceled on March 1, 1919, after 65,000 devices, 1.6 million magazines, 65 million cartridges, and 101,775 modified Springfield rifles had been made. Declared surplus in 1931, nearly all stored devices were destroyed by the Army to prevent them from falling into criminal hands, with only a few kept by the Ordnance Department.
- Introduced
- 1991 (FN P90), 2001 (Heckler & Koch MP7)
- Cartridges
- FN 5.7×28mm, HK 4.6×30mm
- Magazine capacity
- 50 rounds (FN P90), 20-, 30-, 40-round (H&K MP7)
- Weight
- 1.9 kg (4.19 lb) with empty 20-round magazine (H&K MP7)
- Action
- Blowback (FN P90), short-stroke piston gas system (H&K MP7)
- Countries used
- Over 40 countries (FN P90); Austria, France, Germany, Ireland, Norway, Malaysia, United Kingdom (H&K MP7)
Lore & Background
The concept of a compact defensive firearm for non-frontline troops has historical precedents. In the late 19th and early 20th centuries, shortened rifles called carbines were issued to cavalry and gun crews. During World War I, the Pedersen device allowed the M1903 Springfield rifle to fire a pistol cartridge in semi-automatic mode, effectively converting it into a form of submachine gun. Production of 65,000 devices and modified rifles began in 1918 but the war ended before deployment, and most were destroyed by 1931. In 1918, the Chauchat-Ribeyrolles 1918 submachine gun was designed for French tank crew protection but was deemed too powerful for self-protection. In 1940, the U.S. developed the M1 Carbine and later the select-fire M2 Carbine as a lighter alternative to the M1 Garand for support troops. The modern PDW concept emerged with the FN P90 in 1991, a bullpup design with a 50-round magazine and integrated reflex sight, firing the 5.7×28mm cartridge capable of penetrating soft body armor. The Heckler & Koch MP7 followed in 2001, using a short-stroke piston gas system and firing 4.6×30mm ammunition, also capable of penetrating soft body armor.
Reader's Guide
The personal defense weapon concept has not been widely successful for its intended application. Existing PDWs are not significantly cheaper to manufacture than carbines or full-size military rifles, and most use proprietary cartridges such as the 5.7×28mm or 4.6×30mm, which were not originally compatible with existing pistols or rifles. Although both FN and Heckler & Koch planned handguns using their respective rounds, only FN produced the Five-SeveN pistol, leaving the 5.7×28mm without a handgun option for over two decades until the Ruger-5.7 in 2019. This lack of mass production made PDW cartridges expensive for consumers. Despite limited adoption for their original role, PDWs have been acquired by various military special forces units and law enforcement groups as an upgrade for older submachine guns. The FN P90 and Five-seven pistol are used by military and police forces in over 40 countries, including Canada, France, Greece, India, Poland, Spain, and the United States. The Heckler & Koch MP7 is used in Austria, France, Germany, Ireland, Norway, Malaysia, and the United Kingdom. Carbines remain widely preferred for the roles PDWs were designed to fill.
Did You Know?
- The FN P90 was designed to have a length no greater than a man's shoulder width for easy carry in tight spaces like armored vehicles.
- The Heckler & Koch MP7 weighs only 1.9 kg (4.19 lb) with an empty 20-round magazine due to heavy use of polymers.
- The Pedersen device of World War I allowed conversion of an M1903 Springfield rifle to fire the .30-18 Auto cartridge in semi-automatic mode in about 15 seconds.
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