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Coldwar American Prototypes

M-70 Main Battle Tank

USA (1962 – 1963) – MBT – None built

In 1962, the US Armor Association launched a competition for the design of a next generation of Main Battle Tanks (MBTs) to replace the M60 Gun Tank in light of advanced Soviet vehicles which were being developed. The goal was to gather ideas as to how people thought the tanks of 1965-1975 might look and left the various designers a lot of freedom in terms of armament and propulsion. Many designs were sent in from around the world but one very close to home came from a serving US soldier, David Bredemeir, based at Fort Knox, the home of the US School of Armor at the time. This design was to eschew conventional suspension, layout, and armament and produce a missile carrier capable of destroying any future Soviet threat. Named the ‘M-70’ (no connection to the MBT-70), presumably for the anticipated in-service date, this vehicle provides a semi-professional glimpse at some of the thinking of the era.

PFC David Bredemeir, the designer of the M-70. Source: Armor Magazine

Layout

The basic layout of the M-70 was a long slender tank. The engine, a “long slender gas turbine”, was positioned alongside the driver at the front. The turbine would power the front-mounted transmission.

Armament

The M-70 was not to be a conventional gun tank. Bredemeir eschewed the conventional cannon approach for his design and put the offensive capability for the tank in the hands of anti-tank guided missiles. This design choice was based upon the logic that it would be able to fire before an enemy tank could and to ensure a first-round hit each time. The result was that the tank was to carry a battery of 8 anti-tank guided missiles (ATGM) in each ‘fender’, the sponsons along each side above the tracks. As the missiles traveled slower than a conventional shell, they could be fired in the general direction of the enemy even without aiming, with this process then being picked up by means of the guidance as the vehicle stopped. There would then be time to guide the missile onto its target before the corresponding enemy tank had had time to stop, aim and fire its main gun. Another launcher was retained in a rotatable turret at the back of the vehicle and between 50 and 60 missiles could be carried. Storage was facilitated for them, as their fins were all spring-loaded to fold down. Of those 50-60 missiles, 20 were to be stored in the turret.

Various types of missiles were proposed, including smoke, chemical, heat-seeking, and even atomic rounds, guaranteeing these missiles were capable of taking on even the heaviest of enemy armor. The heat-seeking missiles also enabled this tank to counter enemy aircraft and it could track them itself too with a built-in onboard radar. A machine gun was mounted on the commander’s cupola.

Crew

The M-70 was to use a three-man crew consisting of commander, gunner, and driver, although the gunner also served as a radar operator. When the gunner was busy loading the missile tube, the commander could take over his duties. Of the three crew, the driver would be at the front, leaving the commander and gunner in the turret at the back. The gunner, situated on the left, would be able to operate the missile launch-tube centrally as well as the radar, and when he was otherwise engaged, the commander could take on the gunner’s duties. The commander sat in the turret on the right-hand side and had his own cupola with a machine gun.

Bredemeir’s M-70 tank design relied upon its low profile for protection and missiles for its firepower. Source: Armor Magazine

Armor

Being lower than the M60 Gun Tank would give the M-70 a higher chance of survival on the battlefield, as it would be less likely to be hit. It also meant a lighter and more maneuverable tank but it still needed armor. The result was that the M-70 was to be made out of aluminum. This, in turn, would keep the overall weight down to 20 to 25 tons (18.14 to 22.70 tonnes)

Suspension

The suspension for the M-70 was a ‘two-stage’ system, with the tracks and road wheels divided in half and connected together via a single leaf-spring holding them to a beam that ran the full length along each side. Each of those beams was then connected by a pivot arm at the front and back of the tank to a connector on the opposite side. The hull itself was not mounted directly to these track units but held via coil springs from each end of the beam instead. Only the driving axles for the sprockets would directly link the hull to the tracks units. This double-spring system was felt to provide maximum comfort. Small road wheels would spread the weight of the tank along its track and also serve to keep the overall height of the vehicle down.

Conclusion

During the 1960s, faced with the enormous growth in power of anti-tank guided missiles, many were speculating it meant the end of the conventional tank. Likewise, the potential of ATGMs outstripped the anti-armor potential for large caliber guns with the advantage of being significantly smaller and lighter. Many countries would consider and even develop ATGM-based tanks during the Cold War, but just like the US Army, they were constrained by budgets, thinking, and a conservative attitude of trying to keep developments relatively simple. The M-70 offered superior firepower to the M60 in a much smaller vehicle but in 1962, this gun-launched missile concept was already underway on the M551 Sheridan. It was never to work satisfactorily for that tank and the M-70 offered little to warrant development.

Illustration of the M-70 Main Battle Tank by Andrei ‘Octo10’ Kirushkin, funded by our Patreon Campaign

Sources

Armour Magazine January-February 1963

M-70 Specifications

Total weight, battle ready 20 to 25 tons (18.14 to 22.70 tonnes)
Crew 3 (Commander/Gunner, Gunner/Radar Operator, Driver)
Propulsion Petrol turbine (fuel tanks under turret at the back)
Armament ATGM launchers, 50-60 shells (incl. 20 in turret)

5 replies on “M-70 Main Battle Tank”

I disagree that missile based guns like on M70 would never work satisfactory performance. Sheridan had issues with having too powerful cannon for its size. That issue would not be present on bigger, more sturdier vehicle.

I do believe that tanks like that is something which could had been great addition to world military across the globe. Nowadays we do not have solution to the problem which these missile tanks provide. How to make a light tank small and capable enough to engage MBT while still retaining advantages of a light tank. Americans had tried and failed with Bulldog and M8. They had excellent Sheridan, but it was put out of service without ANY replacement. Hence, USA armed forces have notorious problems of actually deploying abroad as it takes too much time to deploy Abrams into a conflict zone.

Such missile tanks could solve both of the problems, taking away need to put heavy and recoil intensive cannons on light vehicles and allowing them an effective firepower against soft and hard targets. The real and essential problem when designing a light tank is fitting into 17-19 ton deployment limit for airborne operations or keeping weight down for inherent amphibious capabilities. Putting 105 mm traditional gun not only makes vehicle incapable of effectively fighting other MBT, but also weight of a gun drastically lowers effective protection of a vehicle (resistant only to machine gun fire) or/and increases drastically weight into effective 20 ton range.

Sheridan tank was 15 tons. This prototype was to be around 5 tons heavier. A bigger vehicle would spread stress of its recoil better than a smaller one. I was disagreeing with author that Sheridan gun was problematic. Its missiles were problematic which later were fixed. Another problem was its recoil of 155 mm ish gun on 15 ton aluminium based tank. Gun on that tank was only a problem, because vehicle was too light for its tonnage. USA either needed a slightly heavier, sturdier vehicle like M70 to fix said problem or they needed to develop newer gun which would compensate for its recoil in one of many ways.

As for light vehicle having enough firepower to threaten tanks. Well, it depends on time period. In interwar period we had vehicles such as AMD35 who were a lot lighter, cheaper, quicker and had enough firepower to easily knock out a lot of lighter tanks. Considering that at the time main tank of German forces were Pz.2 with 20 mm autocannon, you do start to question viability of tanks all together.

Later one we had M24 with similar firepower of Sherman. In early cold war we see AMX13 with oscillating 75 mm low pressure cannon. We also have Soviet PT-76, but it relied heavily on HEAT shells to be able to penetrate its targets which have worse ballistic performance. In mid cold war we have such gem like AMX13-105. It could punch way above its weight and threaten MBT of that era. We have introduction of Sheridan who utilize rockets and HEAT shells who were very dangerous if they would hit enemy armor. In addition, its massive cannon had allowed unparalled anti infantry performance on a light vehicle.

This is where story of light tank ends. In recent years since 80’s MBT had seen rapid increase in effective armor protection. Not only in composite armor, but in general, newest generation tanks had a lot more armor on them by design than tanks of previous generation. This had meant that light tanks had to upgrade their firepower together with MBT to stay relevant. However, we did not seen any vehicles or serious efforts from Western powers to create a proper light tank. A lot of our light tanks either are under-armed with 105 mm cannon or are too heavy, big for airborne/amphibious operations. Stingray is a nice example of how potentially decent tank is just little bit too heavy. The only proper light tank which comes to my mind is 2S25 Sprut-SD. It is light, airborne, amphibious, mobile and most importantly, it has firepower to seriously threaten MBT.

The main problem of why vehicle class specifications like light tank, medium tank, heavy tank are gone is not, because those specifications are no longer valid or those vehicles are no longer potent and useful. It is rather systematic problem of entire system where everyone wants to have a say in vehicle design and procurement and nobody wants to make a compromise. Thus, we get one size fits all – MBT and any other vehicle type gets butchered and made pointless by inability to make those compromises in order to emphasize vehicle’s strengths and its niche role. If you want to know more, watch Pentagon Wars about Bradley. That is an amazing example of how too many cooks in kitchen results in atrocity of a vehicle. Though, said problem is prevalent everywhere to lesser or bigger extent. I remember Leopard and C90 too deviating quite a bit from initial design requirements, but those are more positive examples.

Oh, I had forgot that you said: “tank under 20 tons”. So for the sake of completeness I will add weight of all vehicles which I had references prior.

AMD-35 – 8.2 tons.
M24 – 18.4 tons.
AMX13 – 14.5 tons.
PT-76 – 14.6 tons.
AMX13-105 – 15 to 16 tons. (Can’t find solid source)
Sheridan – 15.2 tons.
2S25 Sprut-SD – 18 tons.

As you see, all these vehicles are under 20 tons and have firepower dangerous to MBT. When you cross magical 20 ton line a lot of inherent light tank strengths disappear. Suddenly there are a lot fewer transports who can transport it and air drop it if any. Suddenly it is too heavy for amphibious operations. In addition, it starts to sink into the ground, making it difficult to operate in rough terrain where normal tanks and vehicles cannot usually go. Weight adds up to additional supply costs, etc.

Light tanks have a role to play in modern battlefield, but they require discipline both from politicians and generals in not making a bloated light tank and proper training and understanding of their vehicles from troops on the ground. Too often vehicles are misused on a ground in roles to which they are not suited for.

There is much to be said about medium tanks like theoretical PL-01. A much lighter tank, protected against anything, but battle cannon rounds and with 120 mm gun. It would be far more economical and superior in low intensity operations than any MBT we possess.

I’m sorry for spamming comment section, but I just realized that I had completely missed your point and had made fool of myself. Either way, I see such discussions and opinions as a way to help potential readers to get more knowledge which they would otherwise would not gain merely by reading technical description of a vehicle.

Define me “proper protection”. I don’t think that light tank can bounce main battle cannon shells under 20 tons. I do think that light tank can bounce such shells in a very limited area like turret’s front when they are under 30 tons if designed for it.

As for 20 ton light tank protection, I deem proper protection as having resistance to autocannon shells and having active/passive protection systems if we would talk about well protected, theoretical light tank.

Here is an example of what I consider as well protected light tank. This tank can achieve frontal protection against 35 mm armor piercing autocannon hits with add on armor packages which would put vehicle still under 20 tons.

https://en.wikipedia.org/wiki/SK-105_K%C3%BCrassier

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