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The Pederson Device: WWI Doughboy's Secret Weapon

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

The Pederson Device: WWI Doughboy's Secret Weapon
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.)

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...

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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.”

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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.

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The Device was issued a metal scabbard, a five-cell canvas pouch for spare magazines and a larger pouch to hold the device when not in use. (Rock Island Auction Co.) (top left). The Model 1903 Mark I rifle has an ejection port on the left receiver wall (top right). Markings on a Pedersen Device and a Model 1903 Mark I rifle.

In use, the rifle’s bolt was removed, and the device inserted into the receiver where it was secured by the magazine cutoff lever; a magazine was inserted, the bolt retracted, and the rifle fired in semiauto mode. Reportedly, the device could be inserted, or removed, from a M1903 rifle in 15 seconds and in no way prevented the rifle from being used as originally intended. Rifles thus modified were designated the U.S. Rifle, Caliber .30, Model 1903, Mark I. In the opinion of many, the device’s biggest shortcoming was the cartridge it fired: Cal. .30 Automatic Pistol Ball Cartridge Model of 1918. It consisted of a rimless, straight walled case 20mm in length topped with an 80-grain FMJ bullet that achieved a velocity of approximately 1,300 fps from the M1903’s longer barrel. But, being it was not designed as a combat cartridge and a round that soldiers would “spray” large quantities of at the enemy, it was considered acceptable. After a series of trials, again held in great secrecy in front of Army brass and members of Congress, the device was approved for issue.

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The .30 Automatic Pistol Ball 1918 compared to a .30 Model 1906 (left). A .30 Pistol Ball 1918 (left) compared to 9mm Parabellum (right).

After observing the trials, an army officer opined as to the device’s (hopefully) effectiveness in marching fire “...a line of soldiers advancing across No Man’s Land firing this device at the enemy trenches as they ran would make it extremely difficult for anyone in the trenches to show his head or any part of his body. Of course, fire while running or walking would not be so accurate, but the tremendous number of shots would more than make up for any inaccuracies and the whole enemy trench system would presumably be smothered with a storm of bullets.” It was also theorized that the Pedersen Device also would be useful as a defensive weapon by soldiers to repeal a close quarters attack on their positions.

General Pershing requested 100,000 of the Devices and modified 1903 Mark I rifles for issue to American troops for use in the proposed massive Allied offensive planned for the Spring of 1919. The initial order was placed with Remington Arms Company on March 1918, again in great secrecy. To conceal the true purpose of the device from the Germans, it was designated as the Automatic Pistol, Caliber .30, Model of 1918. As production and issue of Model 1917 “Enfield” rifles far exceeded that of the M1903, it was decided to design and manufacture a Pedersen Device for the weapon designated as the Automatic Pistol, Caliber .30, Model of 1918 Mark II. Few were ever produced before the war ended.2 There were also plans to produce them for Tsarist Russia’s obr. 1891g Mosin-Nagant, rifle but the ensuing Revolution put an end to those plans. But all the secrecy came to naught when on November 11, 1918, an  Armistice was signed between Germany and the Allies.

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A box of .30 Automatic Pistol Ball Model 1918 made by the Remington Arms Co.

Production of devices continued until March 1919, when the contract was cancelled, after reportedly 65,001 devices and 65 million rounds of 
ammunition were produced which were all put into war reserve. Post-war trials showed that the device and its accessories were cumbersome and heavy and its cartridge underpowered. Realizing that the device had no future in the Army in April of 1931, it was decided to scrap all of the Pedersen Devices. Only few hundred survived which today bring top dollar on the collector’s market. I would like to thank the following for providing information and photos used in this article: Joe Engesser, Joel Kolander, Dan Hudson, Bruce Canfield, Jim Curlovic, and Rock Island Auction Co.

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A “Doughboy” firing a Model 1903 Mark I rifle equipped with a Pedersen Device. (U.S. Army photo)

AUTOMATIC PISTOL, CAL. .30, MODEL OF 1918 

  • Caliber: Cal. .30 Automatic Pistol Ball Cartridge Model of 1918
  • Length: 12.6 in. 
  • Weight: 1 lb., 13 oz. 
  • Magazine: 40 rds. detachable box
  • ROF: Semiautomatic
  1. John Browning once told Maj. Gen. Julian S. Hatcher of U.S. Army Ordnance that Pedersen “was the greatest gun designer in the world.” 
  2. https://smallarmsreview.com/the-pedersen- device-secret-weapon-of-world-war-i/



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