17pdr SP Achilles

Infobox Weapon
name=17pdr SP M10 "Achilles"


caption=
origin=United Kingdom
type=self-propelled anti-tank gun
is_vehicle=yes
length=7.01 m (23.69 ft) "(w/ gun)"
5.97 m (19.6 ft) "(w/o gun)"
width=3.05 m (10 ft)
height=2.57 m (8.43 ft)
weight=29.6 tonnes (65,000 lb)
suspension=Vertical Volute Spring Suspension (VVSS)
speed=51 km/h (32 mph)
vehicle_range=300 km (186 mi)
primary_armament=Ordnance QF 17 pounder (76.2 mm)
50 rounds
secondary_armament=.50 cal Browning M2HB machine gun
420 rounds
armour= 9 to 57.2 mm (0.3 to 2.3 in)
engine=General Motors 6046 Twin Diesel 6-71
engine_power=375 hp (276 kW)
pw_ratio=12.5 hp/tonne
crew=5 (Commander, (3×) gun crew, driver)

The 17pdr Self Propelled Achilles was a British variant of the American M10 Wolverine Tank Destroyer armed with the powerful British Ordnance QF 17 pounder anti-tank gun in place of the standard 3" (76.2 mm) Gun M7. With a total of 1,100 M10s converted, the 17 pdr SP Achilles was the second most numerous tank to see service armed with the 17 pounder gun behind the Sherman Firefly.

The name "Achilles" was however not a war time designation, the tank being called 17pdr M10, or 17pdr SP M10, or even occasionally, Firefly.

Origins

In the wake of Germany's successful 1939-41 campaigns, US armor doctrine had incorporated the idea of fast, lightly armored vehicles carrying dedicated high velocity anti-tank guns as being the most appropriate method for dealing with the fast moving armour spearheads of the German Blitzkrieg. The M10 was based on the chassis of the M4 Sherman and sported thinner but more sloped armour 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 Tank Destroyer, preferably with a 360-degree traversing turret, with armor that would be able to resist the German 50mm at 800 yards and mounting the 17 pounder. However with the arrival of the M10 on the battlefield in late 1942, British plans for a turreted Self Propelled gun were cancelled.

The M10 was first made available to the British in 1943. These vehicles were open topped and mounted a 3" American gun, which was significantly more powerful than the Ordnance QF 6 pounder that mounted British tanks of the period and slightly better than the 7.5 cm KwK 40 used by the Panzer IV and Sturmgeschütz III. When introduced into service in late 1942, the thin but sloped armor provided good protection against the standard 50mm gun mounted on most German tanks and Anti-tank guns, and the 3 inch gun was able to easily defeat all German armor then in theatre except for the handful of Tigers deployed against the Western Allies.

Design

The 17 pdr SP Achilles was little more then a modified M10. The main difference between the Achilles and the Wolverine was the gun. The main armament of the Achilles was the Ordnance Quick Firing 17 pounder, a gun with greatly superior anti-tank performance over the standard American 3" anti-tank gun.

The 17 pounder mounted on the Achilles was able to penetrate some 140mm of armour at 500 meters and 131mm at 1000 meters using standard APCBC (Armour Piercing, Capped, Ballistic Capped) ammunition at a 30 degree angle. When supplied, APDS (Armour Piercing, Discarding Sabot) ammunition could penetrate some 209mm of armour at 500 meters and 192mm at 1000 meters at a 30 degree angle. In comparison the 3" gun on the standard M10 using the same type of ammunition (APCBC) would penetrate 98mm of armor at 500 meters at a 30 degree angle, and 88mm of armor at 1000 meters at a 30 degree angle. Only with HVAP ammunition did the 3" gun compare with the 17 pounder, the ammunition being able to penetrate 140mm at 500 meters at a 30 degree angle, and 127mm at 1000 meters at a 30 degree angle. However HVAP ammunition was in very short supply and it only just compared with the standard 17 pounder ammunition that was available in huge amounts for British tankers.

The only other change carried out on the Achilles was the addition of 17mm thick armor plates welded to the front and sides of the M10 to increase armor protection, as well as a 20mm thick shield fitted to the top of the turret to provide protection from overhead threats that resulted from the M10 having an open top turret.

Production and Distribution

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 Americans had simplified the gun mounting to facilitate the adaptation of the 3" mounting to take the 17 pounder. The British took delivery of some 845 vehicles in 1943, but of the second version of the M10, only the T71 mark could carry the 17 pounder, the T70 mark being designed to only allow the lighter American 3" gun.

The British had planned to convert some 1000 M10s into 17pdr armed variants for Normandy, but for some reason conversions were not started until April 1944. By D-Day 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 D-day meant that many British units went ashore fielding standard M10s rather then 17 pounder armed Achilles, and losses in Achilles units could at times be hard to replace, the crews receiving regular 3" armed M10s as replacements for their lost 17 pdr Achilles much to their dismay.

Achilles as well as standard M10s were distributed to regiments of the Royal Artillery rather then to Armored units. Around 1,650 M10 tank destroyers were received by the British during the war, of these 1,100 were converted by the end of the war.

Combat Use

Unlike the Americans who saw the M10 as a tank hunter, the British viewed the Achilles as a mobile anti-tank gun platform. The standard anti-tank gun given to infantry units in the British Army was the 6 pounder anti-tank gun, a small, light yet effective gun able to defeat the more common German Mark 4s and Stugs with regular ammunition, but not the heavier Tigers and Panthers. The next generation British gun, the 17 pounder anti-tank gun, was an extremely effective gun able to deal with Tigers and Panthers, but at the same time a very heavy and unwieldy weapon that could take over 12 hours to move into position and properly dig in and camouflage. The British knew from experience that the Germans often would immediately launch a counter attack against any taken objectives, and it simply took too long to set up the 17 pounders before the German heavy tanks could overrun the infantry's position.

As a result the British used the Achilles as a quick deploying anti-tank gun, able to quickly reinforce to a position taken by friendly infantry and immediately lay down devastating fire with their 17 pounders on counter-attacking German forces while the slower towed 17 pounders were pulled up and dug in for a more long term defensive presence. This setup also had the additional advantage of somewhat neutralizing the vulnerability of weak armor protection of the Achilles, as being used defensively usually allowed the the Achilles to fire the critical and often lethal first shot at attacking German tanks. Usually the only time the British used the M10 and Achilles offensively was in support of Churchill tank units as they received no 17 pdr armed tanks like Sherman and Cromwell troops did.

Achilles went ashore on D-Day, equipping units of the Royal Artillery and Royal Canadian Artillery in Anti-tank Regiments. Perhaps the most successful action of the Achilles was conducted by 8 Achilles of B troops, 245th Battery, 62nd Anti-Tank Regiment, Royal Artillery attached to the Hamilton Light Infantry during Operation Charnwood. A mixed German force of Mark IVs and Panthers from the 12th SS Panzer Division attempted to regain the town of Buron that had been captured earlier by the Canadians. The 8 Achilles of B troop had however set up in an orchard looking south towards Abbaye d'Ardenne, and were ideally placed when the Panzers began their counter attack. In the brief action, 13 German tanks were knocked out and the counter attack fell apart.

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