A Davis six-pounder fitted to a Royal Aircraft Factory B.E.2c is tested at the RFC’s Machine Gun School at Hythe in November 1916. The gun fired upwards at an angle of 45°, the muzzle being level with the top wing to place the breech within easy reach of the pilot.

In 1917 Vickers Vimy F9146 was fitted with a trunnion-mounted 37mm COW gun in a modified nose section at Brooklands. The Vimy was used in trials with the gun for possible use as a Home Defence machine to counter airships and bombers, but the gun’s length and recoil made it cumbersome and the idea was not adopted.

The “bomber-destroyer” concept, which made a certain amount of sense in the context of the mid-to late 1930s, when British military planners were anticipating swarms of unescorted bombers, was given new life with the introduction of the RAF’s Boulton Paul Defiant turret fighter - although the four guns were of 0-303in calibre.

One approach to obtaining a wide field of fire to destroy bombers from below was that of J. A. Peters, whose three-seat Robey-Peters Gun Carrier of 1916 incorporated nacelles under the top wing, with a Davis six-pounder in each (only in the starboard nacelle here). The sole example, 9498, crashed on its first flight and no more were built.
One of the least-known of British warplanes was surely the Robey-Peters Gun-carrier, designed to have an American Davis recoilless gun in the nacelle on the starboard wing, and a Lewis gun in the port nacelle. Contrary to most published reports, two prototypes of this Rolls-Royce-engined biplane were built. The first, illustrated here, made a sucessful first flight at Bracebridge Heath, near Lincoln, in September 1916 but crashed on its second flight. The second prototype differed in having equal span wings and a fixed fin in addition to the rudder.

Designed to fulfil a similar role to the Defiant, but constricted by stringent naval requirements and its less powerful radial engine, the Blackburn Roc was fitted with the same Boulton Paul Type A four-gun turret as its RAF counterpart. By the time it flew in 1938, British interest in 37mm armament for air-to-air fighting was on the wane.

While the COW gun dominates, the Vickers Type 161 serial J9566 shows that it was far removed from the ‘stick and string’ aerodynamics that the format suggests.

The Vickers Type 161 was designed and built to Specification F.29/27, which called for a single-seat fighter capable of carrying a 37mm COW gun and able to overtake, in the shortest possible time, an enemy passing overhead at 20,000ft (6,100m) at 150 m.p.h. (240km/h). Here the Type 161 is seen under construction, with a dummy gun protruding from the distinctive egg-shapped nacelle.

The Vickers Type 161 (F.29/27), J9566, in its final iteration, complete with military markings, with a revised broader-chord rudder and small fins added to the junction of tailplane and struts. As on its Westland rival, the COW gun was set to starboard, the pilot being provided with a periscopic gunsight. The biplane configuration appeared to be something of a throwback, but the widely spaced high-aspect ratio wings provided excellent climb performance. This modified design is believed to have been designated Type 162.
Built to the same specification as Westland COW Gun Fighter was the Vickers COW Gun Fighter, J9566. It was first flown on January 21, 1931. To improve longitudinal trim 60lb of ballast was carried in the nose.

One of two French Tellier T.3 flying-boats acquired by the RNAS in late 1917, N85 is seen here at the Naval Experimental Air Station at the Isle of Grain, Kent, fitted with a COW gun for armament and camouflage trials. Air firing against moored targets showed promise, and it was thought the gun could be effective against submarines.

In contrast to Bristol’s Bagshot design to Specification 4/24, Westland’s Westbury was a more conventional biplane with stations for COW guns in the nose and aft of the trailing edge. The former incorporated a purpose-built rotating mounting which allowed all-round training. The gun position above the roundel housed a Scarff ring for a single Lewis gun.

Westland’s effort to fulfil Specification F.29/27 was the monoplane COW Gun Fighter, the sole armament of which was a 37mm COW gun mounted with the breech casing in the starboard side of the cockpit and firing forward and upward at an angle of 55'. The sole example, J9565, made its maiden flight in the hands of Flt Lt L.G.Paget in 1931.

Short S.81 “126” at Calshot in 1914, fitted with a Vickers 1 1/2-pounder gun mounted on a strengthened nacelle designed by armament specialist Arthur Camden Pratt. The calibre (shell diameter) of the heavy guns mentioned in this article was 37mm (or higher in some cases), but the weight of the shell varied - hence the use of the term 1 1/2-pounder, for example.
It is reported that when this gun was fired during trials the Short stopped dead in mid-air and dropped 500ft.

The unlovely Bristol Bagshot - originally named Bludgeon by the company - was designed to Air Ministry Specification 4/24 for a twin-engined fighter and was to incorporate 37mm COW guns on trunnion mountings in stations in the nose and aft of the trailing edge. The wide-track undercarriage was fitted with aerofoil-section fairings which acted as an auxiliary wing.

The Bristol Bagshot of 1926 had a span of 70ft. The wings were of multi-spar construction and thus provided data fo much later Bombay Bomber-Transport, which is now in quantity production for the Royal Air Force.
The sole Bagshot, J7767, made its maiden flight in the hands of test pilot Cyril Uwins on July 15, 1927. Although that first flight was uneventful, later test flights revealed the aircraft to be a horror, lateral control being lost at higher airspeeds owing to wing torsional flexibility. Unsurprisingly, no orders for it were forthcoming.