Stridsvagn 103 - History

History

In the mid-1950s the Swedish army put out a contract tender for a new tank design to replace their Centurions. A consortium of Landsverk, Volvo and Bofors responded with a new heavy tank design, known under the codename KRV, fitted with a 155 mm smooth-bore gun in an oscillating turret. However this would be an expensive option and the Army started looking at British, German and American tanks.

Then, in 1956, Sven Berge of the Swedish Arms Administration proposed Alternativ S, a domestic alternative (S standing for Swedish). Noting that the risk of being hit in combat was strongly related to height, he proposed that any new design should be as low as possible. The only practical way to do this was to eliminate the turret (which would also make the tank much lighter and simpler), though in terms of absolute height, this still did not give the Strv 103 any significant advantage. Its most likely opponent, the T-64, was only 2.2 meters in height with its turret versus the 2.14 meters of the Strv 103 (a mere 3.5 inches lower). However, T-64's sacrifice for its low height was an extremely cramped interior. Tanks occasionally deploy themselves into hull-down firing positions, either purpose dug or using the crest of a hill, in order to reduce the exposure of the vehicle to enemy fire. In this firing position the level of exposure is determined by the distance between the bottom of the gun barrel to the top of the turret or vehicle, and the angle to which the vehicle is able to depress the gun barrel. Since the Strv 103 orients the entire tank to depress and elevate the barrel, in a hull down position it has a very low apparent height and subsequent visual profile to the enemy. It could also lower the hull a further 13 cm by adjustment of the suspension.

Berge's design tried to solve the aiming problem through the use of a fully automated transmission and suspension system, which would turn and tilt the tank under the gunner's control. The gun itself would be fixed to the hull. Unfortunately, this made it impossible to use a stabilized gun. As a result, the tank could not accurately move and fire at the same time. However, during the period the S-tank was in service, turreted tanks rarely fired on the move, and especially not when used defensively.

Other features of the tank were also quite radical. The gun, a Bofors 105mm L/62, able to use the same ammunition as the British 105 mm L7, would be equipped with an autoloader allowing a rate of fire of 15 rounds/minute, also allowing the crew to be reduced to two - most designs of the era used a crew of four - gunner/driver and commander. Room was available for an extra crew member, the rear driver/radio operator, who faced the rear of the tank equipped with a complete setup for driving. This allowed the tank to be driven backwards at the same speed as forwards, keeping its frontal armour pointed at the enemy.

The commander and gunner/driver both had the same set of sights and controls to fire the gun and drive the tank. Additionally the tank was powered by two engines, a 240 hp Rolls-Royce K60 opposed-piston diesel for cruising and manoeuvring the tank in aiming, and a 300 hp Boeing 502 turbine for dashing at high speed. This was the first use of a turbine engine in a production tank; the Soviet T-80 and US M1 Abrams would later be built with gas turbines for main propulsion.

The concept was interesting enough that Bofors was asked to build a prototype of the suspension/drive train, which they completed successfully. In 1958 a follow-on contract called for two production prototypes, which were completed in 1961. By this point, the army was so satisfied with the design that an initial pre-production order of 10 was placed in 1960. With minor changes, the S-Tank was adopted as the Stridsvagn 103 (103 from the fact that it was the third tank with a 10 cm gun accepted into Swedish service). Full production started in 1967 and ended in 1971 with 290 delivered. The changes included a new gyro-stabilised commander's cupola armed with a 7.62 mm KSP 58 machine gun, and upgraded frontal armour. A screen, similar to those of the Panzer IV Ausf. J of World War Two, was available to help defeat HEAT rounds; however, it was kept secret for many years and was only to be fitted in the event of war.

The Strv 103 was fully amphibious. A flotation screen could be erected around the upper hull in about 20 minutes, and the tracks would drive the tank at about 6 kilometres per hour (3.7 mph) in water.

One tank in each platoon was fitted with a blade under the front hull that allowed it to dig itself into the ground for added protection.

The Stridsvagn 103 never saw combat and so its design remains unproven. However, for its intended role in the 1960s it had numerous advantages. In 1967, Norway carried out a two week comparative observation test with the Leopard 1 and found that with closed hatches the 103 spotted more targets and fired faster than the Leopard. In April to September 1968, two 103s were tested at the British armour school in Bovington, which reported that "the turretless concept of the "S"-tank holds considerable advantage over turreted tanks". In BAOR 1973, the 103 was tested against the Chieftain tank. Availability never fell under 90% and the final report stated, "It has not been possible to prove any disadvantage in the "S" inability to fire on the move." In 1975, two 103s were tested at the American armour center at Fort Knox. The trial demonstrated the 103 fired more accurately than the M60A1E3, but on an average 0.5 seconds slower.