The Ordnance Quick-Firing 17-pounder (or just 17-pdr)[note 1] was a 76.2 mm (3 inch) gun developed by the United Kingdom during World War II.

Before the QF 6-pounder had entered service, the British predicted that it would soon be inadequate given the increasing armour of German tanks.

However, few tanks were capable of carrying such a large gun due to the size limitations of their turret rings.

An additional box was welded to the back of the turret to take the radio, which was moved to allow for the breech and its recoil.

The British also converted some of their US-produced M10 tank destroyers, replacing the 3-inch (76 mm) M7 gun with the 17-pounder; the resulting vehicles were called 17pdr SP Achilles or just 17-pdr M10C.

Efforts to fit the 17pdr on a Cromwell chassis in a better manner than the ungainly Challenger resulted in the Comet tank.

US forces did however request some Firefly conversions in March 1945 and as many as 18 were converted but the war ended before they were shipped from the UK.

The larger 3" cartridge provided a greater propellant charge compared with normal 75 mm shells.

[6] This has the benefit of greater ease of use on tanks, many of which would not have sufficient turret space to accommodate the breech length and recoil distance of the 17-pounder.

Similarly, the smaller 3"-based ammunition was easier to store and handle in the tank's cramped interior.

While offering greater penetration, the smaller (sub-calibre) tungsten core of APDS was considered to provide less accurate fire than APCBC ammunition at ranges beyond 500 yards.

[13] This was due to the much lesser visible impact of rounds that fell short, making it hard to spot the fall of shot and correct aim.

Muzzle blast was also significant, described by crews of the anti-tank gun variant as resembling a hard slap on the chest.

After the Second World War, it was issued to anti-tank units of the Royal Artillery in the British Army of the Rhine (BAOR) towed by the M3 Half Track.

A custom designed carriage for the 17 pounder comprising: In the immediate post-war era in the Middle East, Arab national armies - Transjordan, Egypt, Syria and Iraq - mainly used British manufactured artillery, including the towed 17-pounder.