.: Pat McCumiskey's Sherman Firefly up-gunned with a 17-Pounder





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"British Up-Gunned Sherman
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Sherman Firefly

From Wikipedia, the free encyclopedia
Sherman Firefly
Sherman firefly bovington 2014.JPG
Sherman Firefly, The Tank Museum, Bovington, UK
Type Medium tank
Place of origin United Kingdom / United States
Production history
Designed 1943
Number built ~2,000
Weight 34.75 long tons (33 tonnes)
Length 19 ft 4 in (5.89 m); 25 ft 6 in (7.77 m) overall
Width 8 ft 8 in (2.64 m)
Height 9 ft (2.7 m)
Crew 4 (Commander, gunner, loader / radio-operator, driver)

Armour 89 mm (turret front)
OQF 17-pounder (76.2 mm) gun, 77 rounds
Flexible .50 (12.7mm) Browning M2 machine gun (generally not mounted); coaxial .30 (7.62 mm)Browning M1919 machine gun, 5000 rounds
Engine Chrysler Multibank (5 x inline-6)petrol or radial engine depending on chassis used
425 hp
Power/weight 11.8 hp/ton
Suspension Coil spring
120 miles (193 km)
Speed 25 mph (40 km/h)

The Sherman Firefly was a tank used by the United Kingdom in World War II. It was based on the US M4 Sherman but fitted with the powerful 3-inch (76.2 mm) calibre British17-pounder anti-tank gun as its main weapon. Originally conceived as a stopgap until future British tank designs came into service, the Sherman Firefly became the most common vehicle with the 17-pounder in the war.

Though the British expected to have their own new tank models developed soon, British Major George Brighty championed the already-rejected idea of mounting the 17-pounder in the existing Sherman. With the help of Lieutenant Colonel Witheridge and despite official disapproval, he managed to get the concept accepted. This proved fortunate, as both the Challenger and Cromwell tank designs experienced difficulties and delays.

After the problem of getting the gun to fit in the Sherman's turret was solved, the Firefly was put into production in early 1944, in time to equip Field Marshal Montgomery's forces for the Normandy landings. It soon became highly valued as the only British tank capable of defeating the Panther and Tiger tanks it faced in Normandy at standard combat ranges. In recognition of this, German tank and anti-tank gun crews were instructed to attack Fireflies first. Between 2,100 and 2,200 were manufactured before production wound down in 1945.


The concept of fitting a 17-pounder gun into a Sherman tank had initially been rejected by the Ministry of Supply's Tank Decision Board. Although the British Army had made extensive use of the American-built Sherman tank, it was intended that a new generation of British tanks would replace it in the anti-tank role. First there was the Cromwell tank, which was expected to use the Vickers High Velocity 75 mm gun; this gun would have had superior anti-tank performance to the US 75 mm and 76mm guns that were mounted in the Sherman. The second was the A30 Challenger which was based on the Cromwell but with the even more powerful 17-pounder gun.[1] These two tanks—and their successors, the Comet and the Centurion, which were already on the drawing board—were to have replaced the Sherman in British service, and so the prospect of spending time and money mounting a 17-pounder on the Sherman was not seen as desirable.[2]

Nonetheless several unofficial attempts were made to upgun the Sherman. The earliest attempt can be credited to Major George Brighty of the Royal Tank Regiment while he was at Lulworth Armoured Fighting School in early 1943. Despite the A30 Challenger undergoing initial trials at Lulworth, Brighty was convinced that the Sherman was a better mount for the 17-pounder. However he was stymied by the turret of the Sherman, which was too small to allow for the very long recoil of the gun. In a rather desperate move, Brighty removed the recoil system and locked the gun in place, thus forcing the entire tank to absorb the recoil, but this was a far from ideal situation and there was no telling how long the tank would have been able to handle such a set-up.[2]

Around June 1943, a colleague of Brighty, Lt. Col. George Witheridge of the Royal Tank Regiment, arrived at Lulworth. A veteran of the North Africa campaign, Witheridge had experienced firsthand the lopsided battles between British tanks armed with 2-pounder guns against Rommel's formidable tanks and anti-tank guns. During the disastrousBattle of Gazala in mid-1942, Witheridge had been blown out of his Grant tank, and though he recovered from his wounds, he was declared unfit to return to combat duty. Instead, in January 1943, he was posted to Fort Knox in the United States for six months to advise on gunnery, where he was "sold" on American tanks.[3] While at Lulworth, Witheridge inspected the A30 Challenger, and "joined in the chorus of complaints" about the tank. Upon looking up Brighty and learning of his attempts to use the Sherman, Witheridge lent his assistance.[1] He advised Brighty on methods to solve the recoil issue.

Not long after, Witheridge and Brighty received a notice from the Department of Tank Design (DTD) to cease their efforts. Unwilling to abandon the project, Witheridge, using his connections with such influential people as Major General Raymond Briggs, former GOC of the 1st Armoured Division in North Africa and now Director of the Royal Armoured Corps, and successfully lobbied Claude Gibb, Director General of Weapon and Instrument Production at the Ministry of Supply, to make it an official ministry project. In doing so, the endeavour was taken out of the hands of the highly enthusiastic and devoted amateurs at Lulworth who had initiated it and given to professional tank developers.[1][4]


Sherman Firefly of 7th Armoured Division in Hamburg, 4 May 1945

It was W.G.K. Kilbourn, a Vickers engineer at the time working for the Department of Tank Design, who transformed the prototype into the tank that would serve the British forces from D-day onwards. The first thing Kilbourn had to fix was the lack of a workable recoil system for the 17-pounder. The 17-pounder travelled 40 in (1.0 m) back as it absorbed the recoil of the blast. This was too long for the Sherman turret.[5] Kilbourn solved this problem by redesigning the recoil system completely rather than modifying it. The recoil cylinders were shortened to allow the turret to take the gun and its recoil, and the new cylinders were placed on both sides of the gun to take advantage of the width of the Sherman's turret rather than be hindered by its height.

The gun breech itself was also rotated 90 degrees to allow for loading from the left[note 1] rather than from on top.[6] The radio which was mounted in the back of the turret in British tanks had to be moved. An armoured box (a "bustle") was attached to the back of the turret to house the radio. Access was through a large hole cut through the back of the turret.

The next problem encountered by Kilbourn was that the gun cradle, the metal block the gun sits on, had to be shortened to allow the gun to fit into the Firefly, and thus the gun itself was not very stable. Kilbourn had a new barrel designed for the 17-pounder that had a longer untapered section at the base, which helped solve the stability problem. A new mantlet was designed to house the new gun and accept the modified cradle. The modifications were extensive enough to require that 17-pounders intended for the Firefly had to be factory built specifically for it.[2][6]

Kilbourn had to deal with other problems. On the standard Sherman tank, there was a single hatch in the turret through which the tank commander, gunner and loader entered and left the tank. However the 17-pounder's larger breech and recoil system significantly reduced the ability of the loader to quickly exit from the tank if it was hit. As a result, a new hatch was cut into the top of the turret over the gunner's position.[7] The final major change was the elimination of the hull gunner in favour of space for more 17-pounder ammunition, which was significantly longer than the 75 mm shell and thus took up more room.

The Firefly had no armour or mobility advantages over the normal Sherman tank, although the gun mantlet was some 13mm thicker.

By October and November 1943, enthusiasm began to grow for the project. The 21st Army Group was informed of the new tank in October 1943.[citation needed] Even before final testing had taken place in February 1944, an order for 2,100 Sherman tanks armed with 17-pounder guns was placed. This reaction was understandable, as the Challenger program was suffering constant delays and few would be ready for Normandy, and even worse, the realization that the Cromwell tank did not have a turret ring big enough to take the new High Velocity 75 mm gun (50 calibres long), so the Cromwell would have to be armed with the general purpose Ordnance QF 75 mm. Thus the Sherman Firefly represented the only available tank with firepower superior to the QF 75 mm gun in the British Army’s arsenal. Not surprisingly, it was given the ‘highest priority’ by Winston Churchill himself.[1]

The nickname "Firefly" is not found in wartime official documents but was adopted due to the bright muzzle flash of the main gun.[8] It was sometimes used at unit level (Brigade/Regiment) war diaries from March 1944, with another nickname being 'Mayfly'. During the war, Shermans with 17-pounder guns were usually known as '1C', '1C Hybrid', or 'VC', depending on the basic mark of the vehicle. In British nomenclature, a "C" at the end of the Roman numeral indicated a tank equipped with the 17-pounder.[note 2]


Loading 17-pounder rounds into a Firefly

The main armament of the Sherman Firefly was the Ordnance Quick-Firing 17-pounder. Designed as the successor to the British QF 6-pounder, the 17-pounder was the most powerful British tank gun of the war, and one of the most powerful of any nationality, being able to penetrate more armour than the 8.8 cm KwK 36 fitted to the German Tiger I or the Panther tank's7.5 cm KwK 42. The Firefly 17-pounder was able to penetrate some 140 mm of armour at 500 m (550 yd) and 131 mm at 1,000 m (1,100 yd) using standard Armour Piercing, Capped, Ballistic Capped (APCBC) ammunition at a 30-degree angle. Armour Piercing, Discarding Sabot (APDS) ammunition could penetrate some 209 mm of armour at 500 m and 192 mm at 1,000 m at a 30-degree angle, which on paper could defeat the armour of almost every German armoured fighting vehicle at any likely range.[citation needed] However, early production APDS rounds lacked accuracy, and the 50 mm penetrator was less destructive after it had penetrated enemy tank armour than the 76.2 mm APCBC shell. In any case, APDS ammunition was rare until late 1944.

The Firefly's superior antitank capabilities notwithstanding, the tank was regarded as inferior to the regular Sherman's 75mm gun against soft targets such as enemy infantry, buildings and lightly armoured vehicles due to its lack of an effective HE round. As the war in Europe neared its close, the Allies found themselves encountering these more often than heavy German tanks. Allied tank units therefore typically refused to completely switch to Fireflies. A good HE shell only became available in late 1944 and even then was not as potent as the standard Sherman 75 mm HE shell.[1] Another problem was that the powerful blast from the 17-pounder gun kicked up large amounts of dirt as well as smoke, making it difficult for the gunner to observe the fall of the shell, forcing him to rely on the commander to observe it and to order corrections. Dirt and dust revealed the position of the tank, so Sherman Fireflies would have to move every few shots. The recoil and muzzle blast could be severely jarring to Firefly crews and the muzzle blast frequently caused night blindness as well. This was a common problem on any tank armed with a high velocity gun, including Panther and Tiger tanks. The cramped nature of the turret meant that loading the large 17-pounder shell was difficult, so Fireflies had a lower rate of fire compared to regular M4 Shermans.[6] Since the Firefly was a stopgap, these problems were never eliminated, as the Firefly was to be retired with the introduction of the new British tank designs.

The Firefly's secondary armament was the standard .30 inch coaxial machine gun in the turret. The hull-mounted machine gun had been removed to increase ammunition storage for the main gun. A top-mounted .50 calibre machine gun was also attached, though many crews removed it due to its awkward mounting and position near the commander, which limited a full 360-degree view when unbuttoned in battle.

With rockets attached to the turret

In 1945, some British Shermans were fitted with a rail on either side of the turret for two "60 lb" (27 kg) high-explosive 3-inch rockets. These were used at the Rhine Crossing by the tanks of a single squadron of the 1st Coldstream Guards. These tanks, called "Sherman Tulips", were conventional Shermans and Fireflies. The rockets, accurate when fired from aircraft, were less accurate when fired from a tank as they were being fired from a stationary point and had little slipstream over the fins. Despite this, the RP-3 was effective when its 60-pound warhead hit the target.[9]

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