The QF 12 pounder 18 cwt gun (Quick-Firing) was a 3-inch high-velocity naval gun used to equip larger British warships such as battleships for defence against torpedo boats.

In World War I four guns were landed for service in the East Africa campaign, on 10 February 1916, and were used until September.

[4] Fourteen of these guns were mounted in coast defence batteries in the 'Middle Line' of the defences of the Firth of Forth when it was established in 1915 (the batteries on Inchcolm (8 guns), Inchmickery (4) and Cramond Island (2).

The document setting out the armaments of the Forth differentiate clearly between the 12cwt and 18cwt types, both of which were in use in the fortress.

[5] The gun fired the same 12.5 lb 3-inch (76 mm) shells as the other British "QF 12 pounder" guns, but used its own larger separate cartridge case to accommodate a larger quantity of cordite propellant.