17pdr SP Achilles
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The 17pdr SP Achilles (officially 17 pounder, Self-Propelled, Achilles) was a British variant of the American M10
tank destroyer A tank destroyer, tank hunter, tank killer, or self-propelled anti-tank gun is a type of armoured fighting vehicle, armed with a direct fire artillery gun or missile launcher, designed specifically to engage and destroy enemy tanks, often wi ...
armed with the British
Ordnance QF 17-pounder The Ordnance Quick-Firing 17-pounder (or just 17-pdr)Under the British standard ordnance weights and measurements the gun's approximate projectile weight is used to denote different guns of the same calibre. Hence this was a 3-inch gun, of which ...
high-velocity 76.2 mm (3-inch)
anti-tank gun An anti-tank gun is a form of artillery designed to destroy tanks and other armored fighting vehicles, normally from a static defensive position. The development of specialized anti-tank munitions and anti-tank guns was prompted by the appearance ...
in place of the M10's considerably less powerful 3-inch (76.2 mm) Gun M7. A total of 1,100 M10s were converted to Achilles, making it the second most numerous armoured fighting vehicle to carry the 17-pounder gun, behind the
Sherman Firefly The Sherman Firefly was a tank used by the United Kingdom and some armoured formations of other Allies in the Second World War. It was based on the US M4 Sherman, but was fitted with the more powerful 3-inch (76.2 mm) calibre British 17- ...
tank. The name "Achilles" was officially a designation applied to both the 3-inch gun and 17-pounder versions (as Achilles I/II and Achilles Ic/IIc respectively) but was little used during the
Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
; at the time, the vehicle was called 17pdr M10, or 17pdr SP M10, or even occasionally, "Firefly". It has since become identified almost exclusively with the 17 pounder version.


Origins

In the wake of Germany's successful 1939–41 campaigns, US armor doctrine had incorporated the idea of fast, lightly
armoured vehicles Military vehicles are commonly armoured (or armored; see spelling differences) to withstand the impact of shrapnel, bullets, shells, rockets, and missiles, protecting the personnel inside from enemy fire. Such vehicles include armoured fighting ...
carrying high-velocity anti-tank guns as the best way to deal with the fast-moving spearheads of the German
blitzkrieg Blitzkrieg ( , ; from 'lightning' + 'war') is a word used to describe a surprise attack using a rapid, overwhelming force concentration that may consist of armored and motorized or mechanized infantry formations, together with close air su ...
. The M10 was based on the chassis of the
M4 Sherman } The M4 Sherman, officially Medium Tank, M4, was the most widely used medium tank by the Military history of the United States during World War II, United States and Allies of World War II, Western Allies in World War II. The M4 Sherman prove ...
but carried thinner although more
sloped armor Sloped armour is armour that is neither in a vertical nor a horizontal position. Such angled armour is typically mounted on tanks and other armoured fighting vehicles (AFVs), as well as naval vessels such as battleships and cruisers. Sloping an a ...
in order to comply with the high-speed requirement for the tank. At the same time, the British had been examining the possibility of designing a low-silhouette self-propelled anti-tank gun, preferably with a 360-degree traversing turret, with armour that would be able to resist the German
5 cm KwK 39 5 (five) is a number, numeral and digit. It is the natural number, and cardinal number, following 4 and preceding 6, and is a prime number. It has attained significance throughout history in part because typical humans have five digits on eac ...
gun fitted to German tanks at 800 yards and mounting the 17-pounder anti-tank gun. However, with the arrival of the M10 on the battlefield in late 1942, British plans for a turreted self-propelled gun were cancelled. During the North African campaign, the British did use self-propelled AT guns such as 6-pdr Deacon. The
Valentine tank The Tank, Infantry, Mk III, Valentine was an infantry tank produced in the United Kingdom during World War II. More than 8,000 of the type were produced in eleven marks, plus various specialised variants, accounting for approximately a quarter ...
chassis was fitted with the 17-pdr to create the
Archer Archery is the sport, practice, or skill of using a bow to shoot arrows.Paterson ''Encyclopaedia of Archery'' p. 17 The word comes from the Latin ''arcus'', meaning bow. Historically, archery has been used for hunting and combat. In mo ...
which was used later in north-west Europe. The armour of the M10 provided good protection against the 50 mm gun mounted on most German tanks and anti-tank guns. The M10 was first made available to the British in 1943. These vehicles were open-topped and mounted a 3-inch (76.2 mm) M7 American gun, which was significantly more powerful than the
Ordnance QF 6-pounder The Ordnance Quick-Firing 6-pounder 7 cwt,British forces traditionally denoted smaller ordnance by the weight of its standard projectile, in this case approximately . The approximate weight of the gun barrel and breech, "7 cwt" (cwt = hundredwe ...
that was mounted on British tanks of the period and was of equal power to the 7.5 cm KwK 40 used by the
Panzer IV The ''Panzerkampfwagen'' IV (Pz.Kpfw. IV), commonly known as the ''Panzer'' IV, was a German medium tank developed in the late 1930s and used extensively during the Second World War. Its ordnance inventory designation was Sd.Kfz. 161. The Panze ...
and
Sturmgeschütz III The ''Sturmgeschütz III'' (StuG III) assault gun was Germany's most-produced fully tracked armoured fighting vehicle during World War II, and second-most produced German armored combat vehicle of any type after the Sd.Kfz. 251 half-track. I ...
.


Design

The 17 pdr SP Achilles was basically a modified M10, the principal difference being the gun. The main armament of the Achilles was the Ordnance QF 17-pounder, a substantially more powerful gun than the 3 in (76.2 mm) M7 mounted on the standard M10. The single top-mounted .50 inch (12.7 mm)
M2 Browning The M2 machine gun or Browning .50 caliber machine gun (informally, "Ma Deuce") is a heavy machine gun that was designed towards the end of World War I by John Browning. Its design is similar to Browning's earlier M1919 Browning machine gun, w ...
heavy machine gun was retained. The 17-pounder mounted on the Achilles was able to penetrate some 140 mm of armour at and 131 mm at using standard Armour Piercing, Capped, Ballistic Capped (APCBC) ammunition impacting at a 30-degree angle. When supplied,
Armour-piercing discarding sabot Armour-piercing discarding sabot (APDS) is a type of spin-stabilized kinetic energy projectile for anti-armour warfare. Each projectile consists of a sub-calibre round fitted with a sabot. The combination of a lighter sub-calibre projectile wit ...
(APDS) ammunition could penetrate some 209  mm (8 inches) of armor at 500 meters and 192  mm at 1,000 meters at a 30-degree angle, though the accuracy of the APDS round was poor during the war. In comparison, the M7 gun on the standard M10 using the same type of ammunition (APCBC) would penetrate 98  mm of armor at 500 m at a 30-degree angle, and 88  mm of armor at 1,000 meters at a 30-degree angle. Only with High-Velocity Armour Piercing (HVAP) ammunition did that gun compare with the 17-pounder, the ammunition being able to penetrate 140  mm at 500 m at a 30-degree angle, and 127  mm at 1,000 m at a 30-degree angle. However, 3-inch HVAP ammunition was in very short supply, whereas the standard 17-pounder ammunition was available in huge quantities for the British. The 17-pounder required a counterweight fitted behind the
muzzle brake A muzzle brake or recoil compensator is a device connected to, or a feature integral to the construction of, the muzzle or barrel of a firearm or cannon that is intended to redirect a portion of propellant gases to counter recoil and unwanted ...
on its long barrel. This gave the Achilles a distinctive appearance compared to the comparatively short-barrelled, brakeless, entirely straight barrel of the M10. Once the Germans discovered the effectiveness of the Achilles' gun on the same M10 carriage as the much less powerful M7 gun, attempts were made to disguise the 17-pounder by painting its brake and counterweight. Two other material changes were made to the Achilles: the addition of thick armour plates welded to the front and sides of the M10 to increase armour protection, and the M10's open turret was fitted with a 20 mm thick shield to provide protection from overhead threats.


Production

The desire to mount the 17-pounder on the M10 was governed by the degree of difficulty involved in mounting the 17-pounder on the tank itself. Luckily for the British, the initial batches of M10s had an easily modified gun mounting to facilitate the future replacement of the older 3-inch M7 gun with the newer
76 mm gun M1 76 or Seventy-Six may refer to: Common uses * 76 (number) * One of the years 76 BC, AD 76, 1776, 1876, 1976, 2076 Places * Seventy Six, Kentucky * Seventy-Six, Missouri * Seventy-Six Township, Iowa (disambiguation), several places Arts, enter ...
. This gun mounting design allowed for the British to replace the 3-inch gun with the 17-pounder gun. The British took delivery of some 845 vehicles in 1943, but of the second version of the M10, only the T71 mark designed to carry the M1 gun could carry the 17-pounder. The British had planned to convert some 1,000 M10s into 17pdr armed variants for Normandy, but for some reason conversions were not started until April 1944. By 6 June 1944, only some 124 M10s had been converted; however, the number of conversions post D-day increased and by the end of the year 816 M10s had been converted, 152 vehicles in November alone. However, the low numbers at the start of the invasion of Normandy meant both that many British units went ashore fielding standard M10s and losses in Achilles units were often replaced by standard 3-inch armed M10s. As a self-propelled anti-tank gun, both Achilles and standard M10s were distributed to and operated by the regiments of the
Royal Artillery The Royal Regiment of Artillery, commonly referred to as the Royal Artillery (RA) and colloquially known as "The Gunners", is one of two regiments that make up the artillery arm of the British Army. The Royal Regiment of Artillery comprises t ...
. Around 1,650 M10s were received by the British during the war, with 1,100 converted to the 17-pdr by its end.


Operational use

The standard anti-tank gun used in infantry units in the British Army was the QF 6-pounder gun a small, light gun able to defeat the more common German Panzer IV and Sturmgeschütz with regular ammunition but not the heavier
Panthers Panther may refer to: Large cats *Pantherinae, the cat subfamily that contains the genera ''Panthera'' and ''Neofelis'' **''Panthera'', the cat genus that contains tigers, lions, jaguars and leopards. ***Jaguar (''Panthera onca''), found in Sout ...
and Tigers front on. The next generation British anti-gun, the 17-pounder, was able to deal with Tigers and Panthers but had a far longer emplacement time prior to battle than the 6-pounder due to its larger size, often taking a day to fully prepare for action. As a result, the British used the Achilles as a quickly deployable anti-tank gun, able to reinforce a position taken by infantry and engage counter-attacking German forces while the slower towed 17-pounders were pulled up and dug in for a more long-term defensive presence. This had the advantage of mitigating the weak armour protection of the Achilles as being used defensively usually allowed it to fire the vital first shot. This was in line with the original design concept of the vehicle, intended to blunt German "blitzkrieg" attack tactics. The M10/Achilles turret had an extremely slow manual only turret rotation, a limited tactical disadvantage when the tank was used only in a defensive role. As such, they had an advantage over the German Sturmgeschütz, which had no turret rotation. However, the Sturmgeschütz's low profile and heavy armour were significant assets that allowed it to be successful in its different tactical environment. Usually, the only time the British used the M10 and Achilles offensively was in support of
Churchill tank The Tank, Infantry, Mk IV (A22) Churchill was a British infantry tank used in the Second World War, best known for its heavy armour, large longitudinal chassis with all-around tracks with multiple bogies, its ability to climb steep slopes, a ...
units, which lacked the associated 17 pdr-armed tanks that
Sherman Sherman most commonly refers to: *Sherman (name), a surname and given name (and list of persons with the name) ** William Tecumseh Sherman (1820–1891), American Civil War General *M4 Sherman, a tank Sherman may also refer to: Places United St ...
and
Cromwell tank The Cromwell tank, officially Tank, Cruiser, Mk VIII, Cromwell (A27M), was one of the series of cruiser tanks fielded by Britain in the Second World War. Named after the English Civil War-era military leader Oliver Cromwell, the Cromwell was th ...
units had. Achilles went ashore on D-Day, equipping units of the
Royal Artillery The Royal Regiment of Artillery, commonly referred to as the Royal Artillery (RA) and colloquially known as "The Gunners", is one of two regiments that make up the artillery arm of the British Army. The Royal Regiment of Artillery comprises t ...
and
Royal Canadian Artillery , colors = The guns of the RCA themselves , colors_label = Colours , march = * Slow march: "Royal Artillery Slow March" * Quick march (dismounted parades): "British Grenadiers/The ...
in Armoured Division or Corps Anti-tank Regiments. A typical A/Tk Regiment would have 4 Batteries, 2 x Towed 17 Pdr Batteries, 1 x Achilles and 1 x M10 Battery. The M10 Battery was replaced by a second Achilles Battery as more vehicles became available. Perhaps the most successful action of the Achilles was conducted by B troop, 245th Battery, 62nd Anti-Tank Regiment, Royal Artillery attached to the Royal Hamilton Light Infantry during
Operation Charnwood Operation Charnwood was an Anglo-Canadian offensive that took place from 8 to 9 July 1944, during the Battle for Caen, part of the larger Operation Overlord (code-name for the Battle of Normandy) in the Second World War. The operation was int ...
. South of Buron, a counterattack by a mixed force of Panzer IV and Panther tanks of the 12th SS Panzer Regiment was defeated by Achilles and 17-pounder anti tank guns of 245th Battery, 62nd Anti-tank Regiment. Thirteen German tanks were destroyed in one of the most successful antitank engagements of the campaign, for the loss of four self-propelled guns and a further four damaged.Copp (2003), pp. 103–104, 296–297


Surviving examples

File:M10 (17pdr) Achilles Ic (35807817713).jpg, 17pdr SP Achilles on display at
The Tank Museum The Tank Museum (previously The Bovington Tank Museum) is a collection of armoured fighting vehicles at Bovington Camp in Dorset, South West England. It is about north of the village of Wool and west of the major port of Poole. The collection ...
,
Bovington Bovington Camp () is a British Army military base in Dorset, England. Together with Lulworth Camp it forms part of Bovington Garrison. The garrison is home to The Armour Centre and contains two barracks complexes and two forest and heathland tr ...
UK File:17-pounder Achilles SP Tank Destroyer, 3rd Cav Museum, Fort Hood, Texas (1).jpg, At the 3rd Cavalry Museum,
Fort Hood Fort Hood is a United States Army post located near Killeen, Texas. Named after Confederate General John Bell Hood, it is located halfway between Austin and Waco, about from each, within the U.S. state of Texas. The post is the headquarters ...
,
Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
File:M10 Achilles self-propelled gun outside the Bastogne Historical Centre.jpg, Displayed outside the Bastogne War Museum


See also

*
Archer (tank destroyer) The Self Propelled 17pdr, Valentine, Mk I, Archer was a British tank destroyer of the Second World War based on the Valentine infantry tank chassis fitted with an Ordnance QF 17 pounder gun. Designed and manufactured by Vickers-Armstrongs, 655 w ...
- a 17 pdr gun in a fixed position on a Valentine tank chassis. *
M36 tank destroyer The M36 tank destroyer, formally 90 mm Gun Motor Carriage, M36, was an American tank destroyer used during World War II. The M36 combined the hull of the M10 tank destroyer, which used the M4 Sherman's reliable chassis and drivetrain combine ...
- an American 90mm gun upgrade of the M10


References


Further reading

* {{WWIIBritishAFVs World War II tanks of the United Kingdom
Sherman Sherman most commonly refers to: *Sherman (name), a surname and given name (and list of persons with the name) ** William Tecumseh Sherman (1820–1891), American Civil War General *M4 Sherman, a tank Sherman may also refer to: Places United St ...
World War II tank destroyers Military vehicles introduced from 1940 to 1944