A34 Cossack - A Russo-British A15 Replacement
Under the Anglo-Soviet Military Supplies Agreement of 27 June 1942, Britain pledged to supply Stalin with armaments free of charge. This included British- and Canadian-made tanks (and other armoured vehicles). However, what the Red Army really needed in those dark days was increased numbers of their own, most-favoured T-34 medium tanks. Accordingly, an addenda to the June 1942 agreement made arrangements for T-34 plans and hardware samples to be provided to Britain to enable licensed T-34 production. As Nuffields had relevant Christie suspension experience, production of British T-34s was assigned to Ward End. But this production effort was not without its challenges.
In early October 1942, a sample T-34 hull arrived by rail at Birmingham having been shipped by Arctic Convoy from Archangelsk to Liverpool. Problems arose immediately. The early-model sample T-34 hull was essentially empty. Neither turret nor Kharkov V-2 diesel engine were included. Inquiries revealed that the Soviets would be unable to supply such items to Britain - the Red Army's immediate needs were simply too pressing. That left the design team at Ward End to their own devices. A quick study showed that the A15 turret would easily fit on the T-34. [2] Likewise, the Crusader's Rolls-Royce Rail V-12 and transmission fit the T-34 hull. However, the A15 turret was rejected as obsolete by the Soviets and, in reality, the 340 hp Rail lacked sufficient power for this heavier vehicle.
The solution to engine power proved relatively simple. Rolls-Royce informed Nuffields that, with supercharging, its Rail could easily match the Soviet diesel's output of 500 hp. That left the problems of turret and armament. The Matilda II's well-protected, cast turret fit but its 2-pounder (40 mm) armament was judged out-of-date. Fortunately, a larger turret with the same turret-ring size had just become available. This was the turret from the recently introduced Churchill Mk.III, armed with a high-velocity 6-pounder main gun. This weapon was of much smaller calibre than that Red Army T-34 guns - the 76 mm F-34s - but this was acceptable to the Soviets. [1] Shipments began of what the Red Army called the T-34 britanskiy birmingem. These 6-pounder armed T-34bb vehicles were adopted by the Red Army as tank-istrebiteli (or tank destroyers). [2]
Top An early Nuffield-built T-34 britanskiy birmingem in Red Army service as a tank destroyer, Spring 1943.
Once shipments of Nuffield-built T-34s were underway, the Director of the Royal Armoured Corps also expressed interest in the vehicle. Prior to export, some T-34s destined for the Soviet Union were successfuly tested at the RAC Centre at Bovington. As a result of these Dorset trials, the War Office requested transfer of some Nuffield T-34 production to the RAC under the designation A34 Cossack. The British Army knew the loaned T-34bb as the A34 Cossack Tank, Heavy Cruiser, Mark Is. The 'Anglicized' production variant was the A34 Cossack Mk.IA. The slightly later A34 Cossack Mk.IIA [4] was a purely experiment model - essentially a Mk.I hull fitted with the Raptor V-12 diesel engine from the T-34bd (Britanskiy dizel'. [3] This powertrain concept was then 'productionized' as the A34 Cossack Mk.III.
After the first British encounters with Germany's huge Tiger tanks, the pressure was on for up-gunned Cossacks. [5] The first in service was the A34 Cossack Mk.IVA armed with a Royal Ordnance QF 75 mm gun - a 6-pounder bored out to accept US 75 mm shells in 'necked' cartridges. The result was greater HE capacity shells but at much-reduced velocity (620 m/s - versus 1,082 m/s for 6-pounders firing APCR rounds). Other than in the calibre of its main gun and the design of ammunition stowage racks, the A34 Cossack Mk.IVA - being Raptor-engined - was virtually unchanged from the preceding, 6-pounder armed Mk.III. For the first time, the RAC was given priority on Cossack delivery. Only later would the Red Army receive QF 75 mm-armed A34 Cossack Mk.IVs built to Soviet standards.
The ultimate gun for the A34 Cossack series was the Vickers 75 mm L/50 HV. This piece also fired US 75 mm shells but from a much larger and more powerful cartridge. However, whereas the RO QF 75 mm fit within the A34's Churchill III turret, the bigger 75 mm L/50 HV would not. As a result, an entirely new turret was needed. At a glance, the turret of the A34 Cossack Mk.V looked like an extended A34 Mk.III turret. It wasn't. Sitting on a 'full-sized' 1,425 mm turret ring, the new turret was larger overall to accommodate the Vickers gun. [6] There were no Mk.V variants deliveries to the Soviet Union. Ward End production of the Mk.V was quickly eclipsed by the A34 Cossack Mk.VA which eliminated the bow machine gunner's position in favour of greater 75 mm ammunition stowage space.
Bottom Royal Tank Regiment A34 Cossack Mk.VA deployed in Normandy, July 1944. For greater protection, the crew of this otherwise near-pristine Cossack have welded tank tread sections (likely from a Churchill) to their turret sides. Note the Vickers-gunned tanks' distinguishing features - lengthy gun with muzzle brake, sloped mantlet, and longer turret rear 'bustle'.
(Fin)
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[1] The 6-pounder tank gun had a muzzle velocity of 892 m/s (with early armour-piercing rounds) versus only 680 m/s for the Soviet 76 mm F-34. Ideally, the T-34bb tank-istrebiteli and 76 mm-armed T-34s acted in concert. The T-34bb would be the dedicated 'hole puncher' while the T-34/76 performed the close-support role.
[2] In this role, the British-built vehicles made the Red Army's domestically-produced tank-istrebitel' - the T-34-57 - redundant. This allowed Soviet production to focus on 76 mm-gunned T-34s. However, some Nuffield tanks were rearmed locally with the T-34-57's longer ZiS-4 main gun and the ZiS-4 would also be fitted to T-34bb/57s (see below).
[3] The Red Army was anxious for diesel power for fuel commonality with their domestically-produced T-34/76 fleet. (The full Soviet designation was T-34bb(dd) for Britanskiy-Birmingemskiy dizel'nyy dvigatel' but, in Red Army usage, this was invariable truncated to T-34bd.) The Raptor was a development of the Rail incorporating diesel elements from the Nuffield-built Roadrunner 6-cylinder engine.
[4] Mk.II was a British admin designation for the T-34bb/57 - a Mk.I delivered with its turret adapted to take high-velocity Soviet guns upon arrival (these being 57 mm ZiS-4 L/73 cannons).
[5] Lucky shots from a Churchill's 6-pounder were able to disable a Tiger at Robaa, Tunisia, in February 1943. The similarly-armed Cossack Mk.IA was not ideal but its well-sloped hull was, at least, better-protected than that of Churchill.
[6] The A34 Cossack Mk.V series turret ring size was the same as that of the original T-34/76. Since the earlier A34s had removable spacer rings, in theory, any early-model A-34 could be upgraded with the larger turret.