Sweden Sweden (1956)
Main Battle Tank – 290 built

The “S-Tank”, a historical landmark?

The Strv-103 is one of a kind, concentrating so many innovative solutions and new ideas into one vehicle, that to this day it has left an unmistakable imprint in tank design, according to most experts. It was a rather original solution to the unique national defense issues of Sweden during the cold war. Sweden chose to adopt the tank best suited for the landscape it was to fight on, this, in turn, produced an unconventional solution: a self-propelled gun used as a main battle tank, classed and recognized as one despite its obvious lack of a turret. It succeeded in this category by concentrating many technological breakthroughs that rendered this paradox possible.

Strv-103 at the Saumur Museum

Development of the Strv-103

In the mid-1950s, the standard Swedish MBT was the British-built Centurion (Stridsvagn 81 to 104). But there were already proponents pushing for its replacement with a domestic tank. The consortium Landsverk, Volvo and Bofors proposed the KRV tank design, using a 155 mm smoothbore into an oscillating turret. It was eventually rejected as it was deemed to be too expensive, and the government turned once more to foreign designs. In the meantime, Sven Berge (of the Swedish Arms Administration) proposed the “Alternative-S” model based on the lowest possible silhouette, which would be far cheaper than the KRV and even some foreign designs. This design eliminated the turret, and the problems of gun elevation and depression found in vehicles without turrets were solved in an unorthodox way.

Berge came up with the idea of a fully automated suspension able to provide vertical motion to the gun, assisted by an automatic transmission. After the plans were submitted, Bofors was asked to build a prototype of the suspension and drive train, which was then successfully tested. In 1958 came an order for two first production prototypes which were completed in 1961. In the meantime, the army ordered an initial pre-production batch of ten tanks. After a few modifications, the “Alternativ S” was put into service as the Stridsvagn 103 (the number stands for being the 3rd tank armed with a 10 cm main gun in service). The full batch production was placed in 1965 and the first deliveries spanned from 1967 to 1971, with 290 machines.

Tank museum Munster

Design

The design was as radical as its roots suggest. Instead of having a standard suspension and some limited elevation and traverse as well as a propensity to strain the transmission when maneuvering like with many casemate-gun vehicles, the S-Tank was given hydropneumatic suspension and a fully automatic transmission. The gun was entirely fixed inside the turret, which allowed the driver in practice to be also the gunner when aiming the gun. The fixed gun also meant that the hull could be made as low as possible. There was a catch, however: this system forbade firing on the move. This was not seen as a great disadvantage, as practice had proven with the Centurion that the best accuracy was obtained while stationary.

The gun, for practical reasons, was a Bofors 105mm L/62, firing the same ammunition as the British 105 mm L7 (50 rounds in store). It had an autoloader (placed at the rear bottom end) to allow a 15 rounds/minute and to reduce the crew to only two. Spent cartridges were ejected through a flap in the rear. The commander normally passed target information to the driver/gunner, which then aimed the gun and fired when stopped, but the commander had duplicate controls and override, plus control over smoke dischargers, in case of need for immediate action. There was enough room for a driver/radio operator facing rearwards, who could drive the tank in reverse if needed, keeping the front armor always pointed to the direction of the enemy.

Consoles were futuristic in appearance and were designed to be ergonomic. For aiming, the tank could traverse smoothly and precisely, despite obstacles in its path, and swivel on its own axis. The elevation/depression range was 22°, better than most MBTs of the time.

In addition, the commander and driver both had the same set of sights but also controls to fire the gun or drive the tank. That also was very specific to the S-Tank. Secondary armament comprised two fixed 7.62 mm KSP 58 machine guns and one anti-aircraft 7.62 mm KSP 58 machine gun placed on the commander’s cupola. A gyro-stabilized cupola model was added during production. In addition, slat armor could be added on the front to help defeat HEAT rounds. This armor was long kept secret.

S-Tank

The hull was indeed also radical, and while it was made of standard RHA, and still relatively thick (90-100 mm on the front glacis) it formed such an angle that the thickness equivalent in direct fire was far greater. The hull could be lowered to a further 13 cm by adjusting the suspension. In addition, it had a folded dozer blade under the front hull to dig itself in the ground (acting also an extra protection). Placing the tank in a hull down position would have given a very little apparent height and quite a limited visual profile to the enemy observers. It was for example 3.5 inches lower than the T-64, but the latter paid for this extremely low silhouette with a very cramped interior.

The Strv-103 was fully amphibious, with a built-in floating screen and could swim after 20-25 min. of preparation. The speed when swimming was around 6 kph (3.7 mph), using the tracks motion to provide some steering. The changes included a new and upgraded frontal armor. Slat armor could be mounted at the front to help defeat HEAT rounds, but it was only to be fitted in the event of war because of its secrecy. Lately, nine jerry cans were added on each side, acting like add-on armor.

The powerplant also was tailored to the hull and was quite original. It was an arrangement of two engines: A flat 240 hp Rolls-Royce K60 opposed-piston diesel for slow cruising and maneuvering when aiming, plus a 300 hp Boeing 502 turbine for high-speed travel and cruising on rough terrain. The latter was found in practice underpowered and soon replaced by a Caterpillar turbine (490 hp) on the B version. This was also the first use of a turbine engine in a production tank, worldwide. With the Caterpillar, the combined output of the powerplant was 730 hp. This provided an 18.3 hp/tonne power-to-weight ratio, a top speed on flat of 50 kph (31 mph) and a 390 km total range (240 miles). The diesel engine was coupled to 2 forward and 2 reverse speeds.The gas-hydraulic hydro-pneumatic suspensions were also very innovative. It served four large coupled rubber-clad roadwheels. There was a drive sprocket at the front and idler at the rear. Due to the narrow space allocated to the nose, the transmission was placed here, right before the driver. This suspension allows the gun (and whole hull) to depress enough in a hull down position that it presents virtually no frontal surface to the enemy while being still capable to spot and destroy opposing targets.

Variants

Strv-103 B

After the 80th tank delivered, operations showed the early production model was somewhat underpowered after all the added modifications compared to the prototype. To keep the performances up, a new Caterpillar 553 turbine was adopted. The latter could deliver 490 hp (365 kW) as compared to Boeing’s 300 hp. The first batch was later called Strv-103A and then upgraded to the “B” standard powerplant.

Strv-103 C

After 15 years of service, it was envisioned an upgrade to keep pace with advances in gunnery in the east. An improved fire control system was installed, but also a dozer blade for all vehicles (one per platoon before). In 1987-88 the aging Rolls-Royce diesel was replaced with 290 hp (216 kW) Detroit Diesel, with additional fuel tanks. The first-hit capability was much improved by the addition of a new laser rangefinder. Reactive or appliqué armor was studied in the early 1990s but this prospect was never carried out as it was decided to retire the model in favor of the Strv-122 (Leopard 2).

Strv-103 D (prototype)

This last upgrade was performed in the mid-1990s, with a new fire-control computer, Gunner & commander thermal sights for low-visibility and night fighting, and a passive light enhancer for the driver. The suspension and engine receive the adjustment and minor modifications. This unique prototype was also even tested under remote control.

4-view drawing

Operational history

The S-Tank was intended to deal with Soviet tanks but also to be suited for suited a landscape alternating rolling farmland in the south and high forests and tundra in the north, frozen or soggy depending on the season. It was to be embedded into earthen ditches, facing the enemy, then retire in fast reverse to join another tactical position. The whole purpose of the “S-Tank” was to fit in a defensive positioning doctrine.

The last Strv-103C was retired in 1997. They were used for training. Nowadays, the single Sstrv-103D and several type C are displayed at the Swedish tank museum Arsenalen, all in running order. The Strv-103 was never tested in combat and never inspired another similar concept, although many of its innovations can be found on modern tanks, like the turbine engine in the M1 Abrams and T-80.

Video: Documentary on the S-Tank

Links about the Strv-103:

The Strv-103 on Wikipedia
Video archive of live test fire (Sw with En subtitles) showing the S-tank protection level

Strv-103 Lynx specifications

Dimensions (L-W-H) 8.99m (7.04m without gun) x 3.63m x 2.43m
(29’5″ (23’1″) x 11’9″ x 7’10” ft.in)
Total weight, battle ready (B/C) 39.7/42.5 tonnes (15 600 lbs)
Crew 3 (commander, gunners, rear driver/radio)
Propulsion RR K60 diesel 240 hp (A-B) Detroit diesel 6V53T 290 hp (C)
Boeing GT502 gas turbine, 300 hp (A) Caterpillar 553 gas turbine, 490 hp (B-C)
Top speed 50 km/h (31 mph)
Range 390 km/290 mi
Armament Main: 105 mm Bofors L/62 50 rounds.
3 x KSP 58 cal 0.3 (7.62 mm) LMGs (1 AA)
Armor From 90 to 100 mm classified (3.5 to 3.9 in)
Production 290

Gallery

S-tank in a public display, 2013S-tank in a public display, 2013S-tank in a public displayS-tank in a public display

Strv-103A

S-Tank of the first serie, 1966.

Strv-103B

Strv-103 B (1970)

Strv-103C

Strv-103 C in the early 1990s

Pansarbandvagn 301
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21 Responses to Stridsvagn 103

  1. WingsOfGlory14 says:

    A TANK…THAT COULD SWIM… O_o
    Now that, is incredible. And No one knew during the War. xD WOW

  2. steppewolf says:

    Last real tank-destroyer…it was a technological achievement and I’m curious how efficient could be a modern variant with 120 mm gun

  3. Vince says:

    The Stridsvagn 103 is classed as an MBT by Sweden. Not a tank destroyer, not an SPG. It may not be a conventional MBT, but that’s how it is in Sweden.

  4. DAVID KNIGHT says:

    Noticed a small mistake. You stated that “The sides were protected by nine composite armor blocks on each side, each block had a handle for ease of replacement and handling.” In actuality those simply are pretty much standard jerry cans attached in series and connected to the fuel system. If you watch the newest “Chieftains Hatch” you can actually get a nice close up view.
    Otherwise I am loving this site!

    • David.B says:

      Fixed, thanks ! In deed at that moment there was no information available about these blocks. It makes much more sense now.

  5. Ray Powell says:

    What’s this obsession with big guns?
    The answer is make it a rocket launcher instead , with fire and forget systems this would do away with complicated suspension system.
    This design is excellent as any Tank with a turret will always have one weakness the turret ring, one jammed makes the tank useless.
    We were taught in the British Army to aim the Turret ring for this reason .

    I know of two tanks defeted this way .

    • Thomas says:

      ATGMs are pretty slow compared to a sabot (for instance the M829 travels at around 1555 meters/sec and the fastest ATGM is only about 900+ meters/sec.
      But if you do give it one like the TOW 2 it would be a pretty good AT platform

      • usmcbandito says:

        As a former tanker and present AT/TOW Squad Leader I can tell you that the gun has the advantage if you are mounting it to vehicle that can handle the recoil. The speed of engagement, time of engagement, and re-engagements, even when not reloading, is much faster compared to TOW. There is also the factor that it is easier (in the majority of frontal engagements) to deflect or stop a heat compared to sabot. Finally gun systems bring more flexibility in the type of ammunition available. From my experience having both would be best. This could be done by creating an extended range version of the Javelin system that could be carried vertical launch style. Since it primarily attacks from the top, armor protection is easier to defeat yet you still have the flexibility of the gun system. Whether or not this is doable yet I do not know but having worked on all of the above systems it seems it would be possible.

  6. usmcbandito says:

    Also I feel the S Tank would be a perfect choice for this type of system especially in the defense since the Javelin system would give it the ability to make the first kill without giving sways its location.

  7. Dexter Blackburn says:

    I am building 2 Swedish MBT strv 103c tanks. I can not seem to find any Swedish tank uniform information. Anyone have any ideas as to what the Swedish tankers of this period wore Thanks to all.

  8. BYSSEMAN says:

    Live fire testing to see how the tank get’s affected on hits from a grenate

  9. Daen says:

    This is defined as a tank in Sweden, but is it actually a tank or tank destroyer? By tank anatomy it would be a SPG, so I was wondering if it is a platypus situation with how it was formed, or if it was called a MBT because it functioned similarly.

    • Stan Lucian says:

      Class is defined by doctrine, not morphology. The Swedes said it was an MBT and used it as an MBT, thus it was an MBT

  10. Joakim Åkerman says:

    Why is this listed as a tank hunter? It’s a MBT. It was designed, used and referred to as a MBT in the swedish army. It was able to perform the same role as other modern, turreted MBT’s at the time in all tests conducted.

    Why is this not listed as an MBT?

    • Stan Lucian says:

      Because we were stupid apparently.
      Fixed a couple of occurences, let me know if you find any more.
      All the best,
      Lucian

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