Davis gun
The Davis gun was a pioneering recoilless cannon invented by Commander Cleland Davis of the United States Navy around 1910, designed to enable the mounting of artillery on early aircraft without the excessive recoil that could damage fragile airframes.[1] It achieved this through a dual-barrel system open at both ends, where a forward projectile was fired simultaneously with a rearward counterweight—typically lead shot or a dummy projectile—to neutralize backward thrust, marking it as the first practical recoilless gun adopted into military service.[1] Primarily developed for anti-submarine warfare during World War I, the weapon was produced in calibers including 1.57-inch (2-pounder), 2.5-inch (6-pounder), and 3-inch (12-pounder), with the 6-pounder variant weighing approximately 126 pounds and featuring a rifled steel barrel equipped with a Lewis machine gun for aiming.[2][3] Development of the Davis gun began around 1910, with Davis patenting the design in 1914 (U.S. Patent Nos. 1,108,715 and 1,108,716), motivated by the need for lightweight, stable armament on naval seaplanes and flying boats.[1] Initial testing occurred at the Naval Proving Ground in Indian Head, Maryland, on October 3, 1912, and in December 1912, demonstrating effective recoil cancellation despite the lower muzzle velocity of about 1,200 feet per second for the 2-pounder shell compared to conventional guns.[2] The British conducted pre-war trials of a 6-pounder version at Shoeburyness and further evaluations from December 1917 to June 1918 on Royal Aircraft Factory F.E.2h aircraft, while U.S. Vice Admiral William S. Sims advocated for its use on seaplanes in August 1918.[1] By the end of World War I, the General Ordnance Company had produced 150 three-inch and 150 six-pounder models, along with 30,000 rounds of ammunition for each caliber, which were deployed on Curtiss HS-2L and H-16 flying boats, Felixstowe F5L seaplanes, and SC-class sub chasers for coastal patrols, although it saw no recorded combat use.[2][3] The gun's performance allowed effective engagement of submarines from altitudes up to 1,000 feet, with tests showing that one fair hit could cripple or sink a U-boat, though challenges like backblast limited its traverse and raised safety concerns for ground crews.[2] Davis resigned from the Navy in 1916 to lead production through his company, and the weapon remained in service until around 1930, influencing subsequent recoilless rifle designs in World War II and beyond, including modern applications by Sandia National Laboratories for testing nuclear components.[1][2]Development and Invention
Background and Invention
The Davis gun emerged during a period of rapid innovation in naval aviation and anti-submarine warfare in the early 20th century. Commander Cleland Davis, a U.S. Navy officer born in 1869 and graduated from the U.S. Naval Academy in 1890, recognized the limitations of conventional artillery in emerging technologies like aircraft and small patrol boats.[2] By 1910, as dreadnought battleships, submarines, and early flying machines reshaped naval strategy, Davis began experimenting with a weapon that could deliver significant firepower without the destructive recoil that threatened fragile airframes or unstable vessels.[1] His work addressed the urgent need for effective armament against German U-boats, which were disrupting Allied shipping lanes ahead of U.S. entry into World War I.[4] The core invention relied on Newton's third law of motion, countering the recoil of a main projectile by simultaneously expelling an equal-mass counterweight from the opposite end of the gun. Davis's design featured a single chamber with two inline barrels: one for the primary shell and the other for the counterprojectile, such as lead pellets or an empty cartridge case, ensuring near-zero net recoil.[1] This principle allowed for lightweight, high-velocity guns suitable for aerial mounting, where traditional recoil could destabilize or damage early biplanes. Initial prototypes, including a 40-mm two-pounder weighing 75 pounds, were developed to test this recoilless operation for both shipboard and aviation use.[2] Davis filed for patents in 1911, receiving U.S. Patent Nos. 1,108,715 and 1,108,716 on August 25, 1914, for his "Apparatus for Firing Projectiles from Aeroplanes" and related mechanisms. Early testing commenced at the Naval Proving Ground in Indian Head, Maryland, on October 3, 1912, and in December 1912, validating the design's efficacy with "no perceptible recoil" observed.[1] In 1916, Davis resigned his commission to lead development through the Ordnance Development Company, refining larger models like 2.45-inch (6-pounder) and 3-inch (12-pounder) variants by late 1916, just before America's declaration of war in April 1917.[2]Patents and Early Testing
Commander Cleland Davis, a U.S. Navy officer, began developing his recoilless gun concept around 1910 to address the challenges of mounting powerful artillery on fragile early aircraft. He filed the first patent application on August 22, 1911, for an "Aeroplane-Gun" (US Patent 1,108,714), granted on August 25, 1914, which described a lightweight gun mechanism designed to minimize recoil through a sleeve-mounted barrel and friable connections that absorbed rearward forces.[5] This was followed by US Patent 1,108,715, filed November 21, 1911, and granted the same day in 1914, outlining a system where the breech block was expelled rearward alongside the forward projectile to balance momentum.[6] A key refinement came in US Patent 1,108,716, filed July 7, 1913, and also granted August 25, 1914, which introduced the core recoilless principle: a barrel open at both ends expelling a compensating mass of equal inertia to the projectile rearward, using disintegratable counterweights like lead pellets in grease or the cartridge case itself.[7] Davis secured a total of six patents for non-recoil guns by 1919, including later applications like US 1,315,630 (filed 1917, granted 1921) for structural integrations in aircraft.[2] Early testing commenced in 1912 to validate the design's recoil-neutralizing capabilities. On a barge off Fisher's Island, New York, prior to April 7, 1912, the gun was mounted on steel springs and fired twice in the presence of U.S. military and naval officers, demonstrating no perceptible recoil and satisfactory performance for aerial applications.[8] Additional ground trials occurred at the Naval Proving Ground in Indian Head, Maryland, on October 3 and early December 1912, confirming the gun's stability and accuracy for aircraft mounting.[1] By 1916, prototypes were evaluated on aircraft, including a 40-mm (two-pounder) model weighing 75 pounds and firing a 1.5-pound shell at 1,200 feet per second, which proved safe without disrupting flight balance; larger 2.45-inch (6-pounder) and 3-inch (12-pounder) variants were also tested for shipboard and aerial use, though challenges like backblast effects emerged.[2] These initial tests paved the way for wartime production, with the U.S. Navy ordering 150 three-inch guns in 1917 following America's entry into World War I, and deliveries beginning in 1918 for subchasers and seaplanes, though no combat deployment occurred before the armistice.[2] The British showed early interest with pre-war evaluations of a 6-pounder version at Shoeburyness, followed by further trials from December 1917 to June 1918 on Royal Aircraft Factory F.E.2h planes assessing anti-submarine efficacy.[9][1] U.S. aircraft-specific tests continued into 1918 on Curtiss HS-2L and H-16 flying boats, recommending further trials for anti-submarine roles.[1]Design and Operation
Principle of Recoilless Operation
The Davis gun achieves recoilless operation through the application of Newton's third law of motion, whereby the forward momentum of the main projectile is precisely counterbalanced by the rearward momentum of an equal-mass counterprojectile, resulting in zero net recoil force on the gun mount. This principle, patented by Commander Cleland Davis in 1914 (US Patent No. 1,108,715), involves a central breech chamber shared by two inline barrels extending in opposite directions, with the forward barrel housing the primary explosive projectile and the aft barrel containing the counterprojectile. Upon ignition of a single propellant charge in the chamber, both masses accelerate equally under the expanding gases, ensuring their velocities at the muzzles are matched in magnitude but opposite in direction.[6] In practice, the counterprojectile often consisted of a non-lethal mass, such as lead pellets embedded in grease or an empty cartridge case, to avoid endangering the mounting platform—particularly critical for aircraft installations—while maintaining the required momentum balance. The physics relies on conservation of momentum, expressed as m_p v_p + m_c v_c = 0, where m_p and v_p are the mass and muzzle velocity of the primary projectile, and m_c and v_c are those of the counterprojectile (with v_c directed rearward). This configuration eliminates the need for heavy recoil-absorbing mechanisms, allowing the gun to be lightweight and suitable for aerial use, though it doubles the effective barrel length and complicates loading procedures.[10] Early prototypes and patents, including US Patent No. 1,108,716, refined this by incorporating a friable breech block or swinging rear barrel section to facilitate the expulsion of the compensating mass, ensuring the gun remained open at both ends for gas venting and recoil neutralization without structural strain on the host aircraft. Subsequent implementations, such as the 6-pounder variant, demonstrated effective recoil cancellation at muzzle velocities around 1,200 feet per second, with the counterweight typically comprising a mass of lead shot mixed with grease such as Vaseline to achieve the necessary momentum balance. This design laid the foundational "Davis principle" for later recoilless weapons, prioritizing simplicity in momentum balancing over exhaustive recoil mitigation hardware.[7][1]Specifications and Components
The Davis gun was developed in multiple calibers to suit aircraft mounting, including a 2-pounder (40 mm), 6-pounder (62 mm), and 12-pounder (76 mm or 3-inch) variant, each designed as a lightweight recoilless system for aerial anti-submarine warfare.[1][11] The 2-pounder measured approximately 10 feet (3.05 m) in length and weighed 75 pounds (34 kg), firing a 1.5-pound (0.68 kg) shell at a muzzle velocity of 1,200 feet per second (366 m/s). The 6-pounder weighed 126 pounds (57 kg), while the 12-pounder reached 210 pounds (95 kg), with a projectile weight of up to 9 pounds (4.1 kg) and a chamber pressure of 15 tons per square inch (2,365 kg/cm²).[2][11] Overall dimensions for the 6-pounder Mark XII variant were 306.1 cm long by 30.5 cm wide by 40.6 cm high, with a total weight of 57.2 kg (126 lb) excluding mounts.[3] Core components included a rifled steel tube barrel serving as both breech and muzzle in an open-ended design, enabling recoilless operation by expelling a counter-mass rearward to balance the forward projectile. Early models featured dual barrels aligned oppositely, with the forward barrel launching the explosive shell and the rear ejecting a counterweight of lead shot approximately equal in mass to the projectile, mixed with grease such as Vaseline for lubrication and reduced fouling. Later iterations, like the 3-inch Mark 15, simplified this by expelling the empty steel cartridge case rearward after firing, clearing the breech automatically.[3][11][9] The system used a central propellant charge in a break-action barrel for loading, with rimmed, keyed cartridges featuring a radial primer for reliable ignition.[2] Auxiliary components enhanced usability in aircraft applications, including a hand grip with dual triggers for firing both the main round and an integrated .30-caliber Lewis machine gun for spotting and aiming. A shoulder rest, U-shaped post mount for swivel yoke attachment, and a rotating rear tube with handle facilitated locking, unlocking, and reloading. Materials comprised primarily steel for the barrel, brass for fittings, aluminum for lighter parts, and leather for grips, ensuring durability under flight conditions while minimizing weight. Sights were basic iron types, with the coaxial Lewis gun providing tracer observation for accurate fire up to 2,000 yards (1,829 m), though maximum range extended to 8,000 yards (7,315 m).[3][2][3][9]| Variant | Caliber | Weight (lbs/kg) | Projectile Weight (lbs/kg) | Muzzle Velocity (fps/m/s) |
|---|---|---|---|---|
| 2-pounder | 40 mm | 75 / 34 | 1.5 / 0.68 | 1,200 / 366 |
| 6-pounder | 62 mm | 126 / 57 | N/A | N/A |
| 12-pounder (3") | 76 mm | 210 / 95 | 9 / 4.1 | N/A |