A Rifle with a Double Life: The Idea Behind the Pedersen Device

Some firearms look like a photo-editing prank at first glance. The Springfield M1903 fitted with the Pedersen Device is one of them: a classic bolt-action rifle with a long magazine jutting out at an angle from the side of the receiver. It is in fact one of the strangest military firearm ideas of the First World War. Swap the rifle's bolt for a special assembly, and you had a self-loading rifle chambered for a pistol-class cartridge. It never saw frontline service.

Historical Background and Development

The Inventor

The device was the work of John Douglas Pedersen (1881–1951). The American designer worked for Remington for many years and later for other companies. He is best known for delayed-blowback designs, including the Remington Model 51 pistol and, later, the Pedersen self-loading rifle in .276. He also worked in John M. Browning's circle.

Trench Warfare as the Catalyst

Trench warfare on the Western Front showed just how valuable short-range firepower could be in close-quarters fighting, in assaults and in trench clearing. The armies went looking for answers: submachine guns (the German MP 18, the Italian Villar Perosa), light machine guns and self-loading rifles. In 1917 the United States had neither a mature submachine gun nor a standardised self-loading rifle.

Pedersen's approach was pragmatic. Millions of M1903 rifles were already in service or in production. If their bolt could be swapped for a self-loading unit, the infantryman could be turned into a rapid-fire shooter in short order. That meant no new rifle and no new production line for an entire weapon.

Adoption and Secrecy

The US Army adopted the system in 1918. The rifle version was designated the "U.S. Rifle, Model 1903, Mark I." The device itself was officially listed as the Pistol, Automatic, Caliber .30, Model of 1918. The name is often described as a deliberate piece of camouflage meant to hide its true purpose. Calling it a "pistol" also fitted the ammunition, which was ballistically closer to a pistol cartridge.

Production figures vary from source to source. You will often read of around 65,000 devices built and a similar number of converted Mark I rifles. The original plans were considerably larger, reportedly running to several hundred thousand units, and in some accounts as many as a million. Anyone who needs exact numbers should compare sources.

Intended Role and Actual Use

The device was meant for a planned offensive often associated with 1919. The infantryman was to be able to switch to self-loading fire in trench and close combat, while normally carrying the rifle with its regular bolt and the .30-06 cartridge. The thinking was simple: at range, the rifle remains an accurate bolt-action; up close, it becomes a rapid-fire weapon with a large magazine.

It never saw action. The Armistice of 11 November 1918 ended the war before the system had reached the fighting troops in any significant numbers. After the war the devices were put into storage and later mostly destroyed, though some stocks were sold off. The Mark I rifles stayed in the inventory as ordinary bolt-actions and can still be identified today by their modified receivers.

Design and Operating Principle

A Swap, Not an Add-On

The Pedersen Device replaced the M1903's bolt. The shooter removed the original bolt and inserted the self-loading unit in its place. In essence this was a complete self-loading breech mechanism with its own magazine housing, firing pin and bolt body. The change took only a few moves and required no tools.

A modified rifle was a prerequisite. The Mark I had an additional cutout in the receiver for ejecting spent cases. There were also changes to parts such as the magazine cut-off and the trigger mechanism. The secondary literature describes the details of these modifications with varying degrees of thoroughness.

Delayed Blowback

The device operated as a blowback action with delayed opening (delayed blowback). The delay came from a mechanical linkage that stopped the bolt from moving freely rearward the instant the shot fired. The cartridge was designed so that this delay was enough and true locking was unnecessary. Cartridges were fed from the side-mounted magazine.

The bullets still travelled down the rifle's own barrel. The device sat in the rear of the action and was fitted to the M1903's chamber. Whether, and to what extent, the details of this chamber adaptation vary by serial number or production lot is not clearly settled in the readily available sources.

Magazine

The magazine held 40 rounds and projected from the receiver at an angle. That was an enormous capacity for the period, but also a bulky attachment. Soldiers were to carry spare magazines in special pouches. Spent cases were thrown out through the additional ejection cutout in the receiver. When the rifle was used with its normal bolt, this cutout stayed open, which in theory could let dirt in.

Calibre and Variants

.30 Pedersen

The device fired the purpose-designed .30 Pedersen (also known as 7.65 × 20 mm). It was a bottlenecked cartridge with a bullet of roughly 5.2 g (80 grains) and a muzzle velocity of about 400 m/s. That puts it roughly in the performance range of the more powerful pistol cartridges. Compared with the .30-06 Springfield (7.62 × 63 mm), it was considerably weaker. Exact figures differ slightly depending on the source.

Variants

There were hardly any true variants of the device. The main distinction concerns the host rifle:

  • M1903 Mark I: the specially modified rifle with ejection cutout and adapted parts.
  • Standard M1903: unsuitable for the device without modification.

Later Pedersen designs, such as the .276 self-loading rifle of the 1920s, are separate weapons and not variants of the device.

Strengths and Weaknesses

Strengths

  • High firepower: self-loading fire with 40 rounds and no reloading.
  • Clever logistics: it used rifles already in service instead of requiring new weapon production.
  • Two guns in one: precision rifle and close-quarters weapon, depending on the bolt fitted.
  • Light recoil: easy to control thanks to the weaker cartridge.

Weaknesses

  • Two types of ammunition: extra logistics and a risk of mix-ups.
  • Shorter range and less effect: the cartridge was designed for short distances.
  • Mechanical complexity: a finely tuned mechanism for the rigours of field service.
  • Bulky magazine: awkward in the trench and during transport.
  • Open ejection cutout: potential fouling when using the normal bolt.
  • No frontline testing: reliability under real combat conditions was never demonstrated.

Rivals and Successors

Several contemporary concepts competed with the device. Bergmann's MP 18 (Germany, from 1918) was a dedicated submachine gun in a pistol calibre. The Villar Perosa (Italy) was an early twin-barrelled weapon in the same calibre class. The US developed the Thompson with similar goals in mind, but it was not ready for service until after the war. Among self-loaders, there were also designs such as the Russian Fedorov Avtomat.

There were no successors in the strict sense. Pedersen's own line led to the .276 Pedersen, with which he took part in the US Army's self-loading rifle trials in the 1920s and 1930s. The winner there was the M1 Garand in .30-06.

Why the System Disappeared

  • The end of the war: the reason for procurement vanished with the Armistice.
  • Peacetime budgets: elaborate special equipment was not pursued.
  • Conceptual overtaking: dedicated submachine guns and, later, self-loading rifles solved the problem more elegantly.
  • A special cartridge: a dedicated round for an accessory was logistically unattractive.

Most devices were destroyed in the years after the war. Surviving examples are therefore extremely rare today and correspondingly sought after by collectors. Mark I rifles, by contrast, turn up far more often. Exactly how many devices survive has not been reliably documented.

Legacy

In the history of technology, the Pedersen Device is interesting above all as a thought experiment. It shows how early people recognised that infantry rifles chambered for a full-power rifle cartridge can be oversized for close range. That thinking led, decades later, to intermediate cartridges such as the German 7.92 × 33 mm Kurz, the Soviet 7.62 × 39 mm and the American .30 Carbine. Whether the device directly influenced these developments is not documented. But it stands at the beginning of the same line of thought.

The principle of converting existing weapons rather than developing new ones also resurfaces later, for example in rimfire conversion kits and interchangeable systems.

Conclusion

The Pedersen Device remains fascinating because it was a radical answer to a real tactical problem: a rifle that could be turned into a rapid-fire weapon with a 40-round magazine in seconds. The fact that it never saw combat makes it something of a "what if" chapter in firearms history. For collectors it is a rarity; for technology enthusiasts it is an example of how early ideas appeared that would later become standard.