The Jagdpanzer SK 105 Light Tank was a tank destroyer developed by Saurer-Werke for the Austrian Army during the Cold War. Its design centered around a capable rifled 105mm main gun armament within a traversing turret assembly atop a lightweight tracked chassis. As a tank destroyer, the SK 105 would naturally be called upon to neutralize enemy armor at range and fill a void in the mechanized forces of Austria - the tank-heavy Soviet Army being the primary enemy of the period. Design work on the vehicle began in 1965 to which a prototype was then completed for testing in 1967 - essentially built up from the preceding Saurer 4K 4FA Armored Personnel Carrier of 1961. Saurer-Werke was then absorbed into the now-defunct Steyr-Daimler-Puch consortium in 1970. The formal designation of the tank became SK 105 "Kurraisser" (sometimes written as "SK-105") and authorized serial production commenced in 1971.
The SK 105 is a tank design of conventional configuration. It features a basic hull with a well-sloped glacis plate, shallow hull superstructure and rear-set engine compartment. The turret is fitted amidships for desired balance when traveling and firing. The hull sits atop a tracked system containing five road wheels to a hull side with the drive sprocket to the rear and the track idler at the front. Three track return rollers guide the track over the road wheels. The vehicle is crewed by three personnel made up of the driver, tank commander and gunner. The driver sits front-left in the hull with the remaining crew in the turret (commander to the left hand side with the gunner to his right). NBC protection is provided for the entire crew and infra-red equipment is located at the driver and commander stations. Armor protection is 40mm at its thickest to help counter the threat from 20mm and smaller fire. Overall weight is approximately 19.5 short tons.
What makes the SK 105 quite unique is its use of an "oscillating" turret design - the Fives-Cail Babcock FL-12 series based on the AMX-13 turret. Oscillating turrets are generally not commonplace in combat tanks but have been successfully utilized in the French AMX-13 Light Tank and Panhard EBR armored car series to name a few. The advantage of such a design lies in the turret being able to fit a heavy, large caliber main gun in a rather modest, lightweight hull configuration. The turret is basically completed as two individual portions - the upper half and lower half with the main gun armament fixed into the upper half, designed to absorb the recoil of the firing action as it moves with it during the process. The upper and lower portions of the turret are hinged with their connection area covered over in visible canvas. As the main gun is fixed to the upper portion, elevation is accomplished by pivoting the entire upper portion of the turret over the lower portion. For traversal, the turret swings to either side in a normal fashion for a complete 360-degree rotation. Turret response functions are powered though an emergency manual system is provided for worse case scenarios.
Primary firepower comes from the aforementioned 105mm rifled main gun. For its time, the 105mm gun system was a proven tank-killer and utilized in many prominent, frontline main battle tank designs of the period. Since the SK 105 crew lacks a dedicated loaded for the main gun, the weapon is reloaded through a pair of "revolver-style" magazines containing six projectiles each. This design configuration allows the required crew to be minimized to three personnel (as opposed to the largely accepted four found in most Western tanks) while keeping the turret dimensionally small. This results in a smaller side and forward profile while lessening construction material and cost. However, reloading requires one of the crewmembers to exit the vehicle to reload the gun through the turret bustle. Spent shell casings are automatically ejected through a door in the bustle. Secondary armament consists of a 7.62mm machine gun in a coaxial mount alongside the main gun. 42 x 105mm projectiles are stowed about the design while 2,000 x 7.62mm rounds of machine gun ammunition are carried. Ammunition types for the 105mm main gun include standard High-Explosive (HE), High-Explosive, Anti-Tank (HEAT), Armor-Piercing, Fin-Stabilized Discarding Sabot (APFSDS) and Smoke rounds. Six smoke grenade dischargers are set in groups of three to each turret side.
The SK 105 internally relies on an in-house Steyr 7FA 6-cylinder, liquid-cooled, 4-stroke, turbocharged, diesel-fueled engine of 320 horsepower. This provides the chassis with a top road speed of 43 miles per hour on ideal surfaces and an operation range of up to 310 miles. The suspension system is of a tried and true torsion bar design. Altogether, the SK 105 provides excellent agility and climbing ratios, making suitable for combat in extremely rugged terrain. The tank can ford up to 1 meter of open water, traverse a 0.8 meter obstacle and cross a 2.41 meter wide gap. Gradients of up to 75% can be tackled.
The SK 105/A1 production models were ultimately upgraded to the new SK 105/A2 standard to which the fire control system (FCS) was replaced and a fully-automatic reloading system implemented for the main gun. The main gun was now stabilized for firing "on the move". The SK 105/A3 mark was a proposed prototype form featuring an all-new oscillating turret design as well as increased armor. This vehicle would have fielded the American M68 105mm main gun which allowed for firing of NATO-standard projectiles. The chassis went on to serve in three distinct though related production forms as the "Greif" ARV (Armored Recovery Vehicle with hydraulic crane, winch and dozer blade), the "Pionier" CEV (Combat Engineering Vehicle) and the SK-105 "Fahrschulpanzer", a turretless trainer derivative.
Since its inception, the SK 105 has gone on to see operational service with the forces of Argentina, Austria, Bolivia, Botswana, Brazil, Morocco and Tunisia in limited numbers. Austria, by far, made up the largest collection of operational SK 105s numbering some 286 examples in service at peak. In all, some 716 SK 105 tanks went on to be produced. The Austrian Army has since given up use of the SK 105 series.
The "Curraisser" name is from the mounted, armored and armed cavalry soldiers featured throughout Europe beginning in the late 15th Century.