The Pedersen Device: WWI Doughboy’s Secret Weapon

Published: 28 May 2024

By Paul Scarlata
via the Firearms News website


The Pedersen Device replaced the bolt of the M1903 rifle turning it into a semiauto rifle with a 40-round magazine. Pedersen’s device was in effect a complete blowback pistol that replaced the bolt. (Rock Island Auction Co.)

The Pedersen Device replaced the bolt of the M1903 rifle, turning it into a semiauto rifle with a 40-round magazine.

Marching fire, also known as walking fire, is a military tactic—a form of suppressive fire used during an infantry assault or combined arms assault. Advancing units fire their weapons without stopping to aim, in an attempt to pin down enemy defenders. Marching fire usually ends with an infantry charge to engage the enemy in close combat. The tactic required ample ammunition and rapid-fire weapons. It differs from fire and movement in that the attacking force advances in unison rather than leapfrogging forward in alternating groups.

The French army first used marching fire during WWI at the Battles of Verdun and the Somme. They used mobile three (later four) man teams consisting of a gunner, a loader and ammo carrier who used the Fusil Mitrailleur Modéle 1915 (“Chauchat”) automatic rifle to take out German machine gun nests.

When the U.S. entered the Great War, our army was almost bereft of machine guns forcing us to purchase large numbers of the Chauchat. American Doughboys quickly formed a low opinion of the French gun and were known to throw them away when they malfunctioned. But the American top brass was enamored with most things “French,” one of which was the concept of marching fire and began training our soldiers to use the tactic.

Enter John Douglas Pedersen…

John D. Pedersen was one of American’s most prolific firearms designers.

John D. Pedersen was born in Denmark, his family immigrated to the USA, settling in Wyoming. In 1907, Pedersen went to work for the Remington Arms Company as a consulting engineer and was instrumental in developing many of their most popular firearms including the Models 10, 12, 14, and 17 shotguns and Models 17, 14, 14.5 and 25 rifles. Pedersen became one of America’s most prolific firearms designers and between 1909 and 1944 received no fewer than sixty-eight patents. (1) But Pedersen’s designs had one shortcoming: while they worked reliably, they tended to be overly complicated. A Remington engineer once confided in me that “Pedersen always used three parts where one would have sufficed.”

A Pedersen Device installed (bottom).

Prior to the United States’ entry into WWI, Pedersen developed a device to dramatically increase the firepower of the M1903 rifle by replacing the bolt with a device consisting of a complete firing mechanism and a small “barrel” for a new .30 caliber pistol like cartridge. In effect, the “device” was essentially a complete blowback pistol minus a receiver-grip using the short rifled “barrel” on the front of the device to fit into the longer chamber of the M1903 rifle. The mechanism was fed by a detachable 40-round magazine which stuck out at a 45° angle from the top, left side of the receiver. The system required an ejection port to be cut into the left side of the rifle’s receiver and the adjacent stock cut away to allow clearance for spent cartridges being ejected the action. The sear, trigger, and magazine cut-off also required modifications. The device was to be carried in a stamped, sheet metal scabbard, and the rifle’s bolt was to be contained in a canvas pouch when it was removed from the rifle. Five Pedersen Device magazines were carried in a five-cell canvas pouch. The metal scabbard and both canvas pouches were designed to be attached to the standard infantry cartridge belt. The device, complete with its carrying scabbard, weighed about two pounds, two ounces, and one fully loaded magazine weighed about one pound.

Read the entire article on the Firearms News website.
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