A prototype upgrade for the STRV-103C. A single 103C was used for the upgrade that added: a fire-control computer,thermal sights for both the Commander and Gunner,and passive lighting for the Driver. Minor suspension and engine changes were made too,and there was talk of adding either Reactive or appliqué armour armor to the tank. But with the introduction of the Leopard 2A4(STRV 121 in swedish service) leased to Sweden,the 103 was withdrawn in 1997,the same year the Leo's arrived and also the last year the 103 was used for crew training.
The upgraded tank prototype still exists along with some 103C tanks on display at Arsenalen national military vehicle museum in Sweden,every tank is still in running order. only 1 STRV 103D was ever made as a prototype. Never saw service Armor is sloped,giving it a LOS thickness of ≈192–337 mm but the actual armor is between 40–70 mm thick. Armament: 10.5cm Bofors L/74 rifled cannon(which was a license built copy of the British 105 L7 cannon. The Swedish version was L/62,which was longer than the L/52 of the British cannon. This gave the Swedish cannon better velocity,accuracy,and more pen),equipped with a 50 round autoloader-system in the rear. 20 rounds on the left side and 25 on the left side. A 5-rnd manual mag was present for other reasons. One side could only hold 1 type at a time,and the C variant had the ability to fire APFSDS and HE shells. (the D variant could fire the same ammo) 4-second reloading. Spent shells eject out the back via a flap. 3 man crew and each crew member could drive and fire the tank from their positions. The tank was uniquely powered via two different kind of engines, a 240 horsepower (180 kW) Rolls-Royce K60 opposed-piston diesel for slow cruising and maneuvering the tank in aiming, and a 300 horsepower (220 kW) Boeing 502 turbine for more power when travelling at higher speed or in severe terrain. The turbine was soon found to be rather weak,so was replaced with a Caterpillar turbine delivering 490 horsepower (370 kW) after 70 tanks were made and was retrofitted to all previous vehicles.
