A plaque, close to the gun, tells us a little about it:
40mm Bofors L.70
Light Anti-Aircraft Gun
Presented to the Borough of Gravesham
on 18 September, 1979, on permanent loan from
The Royal Artillery Institution, Woolwich to
commemorate those light anti-aircraft batteries
which took a vital part in the air defence of
Gravesend during the Second World War.
This website tells us about this model of gun:
"The 40mm L/70 Guns
After the war Bofors sought to build on the success of the 40mm and developed a new and more powerful version, the L/70, which first emerged in 1947 and entered service in 1951. As well as a much higher muzzle velocity, this had modifications to the mechanism to increase the rate of fire; first to 240 rpm, then 300 rpm, and in the latest Trinity version to 330 rpm, thereby maintaining the effectiveness of the AA gun into the jet age.
Breda, who make the Bofors gun under licence, have made further modifications to raise the RoF to 450 rpm in their naval Fast Forty mounting. The modern mountings (both land and naval, as before) are all fitted with a single air-cooled barrel, are power-driven, and feature extended clip frames holding up to 43 rounds to allow a larger ammunition supply for immediate use. The most sophisticated naval versions have a 101-round power-operated magazine. Two of the 40mm guns are shown in enclosed mountings on board the destroyer Småland, shown below left (the big twin turret is the aft 120mm mounting). Weight of a typical four-wheeled land mounting (including on-board generator) is 4,800 kg (see photo below right).
The L/70 guns have found their way into a variety of vehicles, from wheeled and tracked SPAAGs to MICVs. One of the most ambitious efforts was the abortive US Sgt York DIVADS (DIVisional Air Defence) project which featured two guns in a radar-directed turret, all on a tank chassis.
Of even more significance to the lethality of the weapon have been improvements in fire control and ammunition. Although predictor sights were developed in WW2, much shooting was done using the simple 'spider web' open sights. Much more sophisticated systems have steadily been developed, culminating in computerised fire control systems utilising radar target location and aiming. By the 1970s, proximity fuzes were made small enough to fit the 40mm shell (it is still the smallest proximity-fuzed shell in service) and the latest versions have a '3P' round which combines a pre-fragmented HE shell (PFHE) with a programmable fuze. As well as the normal proximity function, the fuze can operate in five other modes: gated proximity (fuze only activated close to the target to avoid premature detonation); gated proximity with impact priority (a slight delay in activation to provide the opportunity for a direct hit); time function (for airburst fire to provide a Shrapnel effect against surface targets); and two impact functions with variable delay. A normal engagement will consist of a burst of fire with the aim automatically shifting between shots to bracket the target.
Other types of ammunition available include Multipurpose, a Raufoss development available in many other calibres which is an HEI round with no fuze - chemicals in the nose are detonated by impact - and for land use in AFVs an APFSDS round capable of penetrating about 150mm of armour.
The Bofors AA gun continues to flourish despite ever-growing competition both from smaller weapons (most recently the 35mm Oerlikon AHEAD system) and from steady improvements in short-range quick-reaction missiles."
The Gravesham Borough Council website tells us about the location where this gun is to be found:
"New Tavern Fort is the remains of an 18th century fort situated within the Fort Gardens and built in the 1780s to defend the Thames against the threat of a naval attack from France. It was extensively rebuilt by General Charles Gordon between 1865 and 1879.
The Fort was re-armed in 1904 and guns representing that period of development are now on display. Come along and venture into the mysterious underground world of the Victorian artilleryman and see the magazines and full size reconstructions of scenes from Gravesend during the Second World War."