M70A2 Krueger MBT, Gulf War, 1991

[Jakko]

In the 1960s, the USA and West Germany started a programme to design the next-generation main battle tank (MBT) for their armies, to replace the current M48s and M60s they were using with something state-of-the-art, able to take on the expected hordes of Warsaw Pact tanks and still come out on top. It was also to be well-protected against nuclear, chemical and biological (NBC) weapons and be able to operate on a battlefield contaminated with them. Furthermore, it was to be built in both countries, with some differences to account for their own preferences.

From the start, the plan was ambitious and ran into all kinds of problems, starting with something as basic as which units to use: the Germans wanted to design and build it in metric, the Americans in their own what-passes-for-a-system. A compromise was eventually reached: each would design the components they were responsible for in their own units, but any mating surfaces and other interfaces would be in metric. Other points of contention were the vehicle's armament (the Americans wanted a 152 mm gun capable of launching missiles, the Germans wanted a conventional 120 mm gun), the engine (Americans: air-cooled diesel, Germans: liquid-cooled multi-fuel), and more. However, they persevered and eventually produced prototypes that proved the project worked:

(The aspect ratio on that video is off, somebody seems to have stretched it to widescreen when it originally wasn't.)

At this point, the vehicle was still known as the MBT 70 (Main Battle Tank 70) in the USA, and as the KPz 70 (Kampfpanzer 70) in West Germany. The videos show many of the tank's advanced features: high mobility from a powerful engine and a hydropneumatic suspension that gave a smooth ride and allowed the tank's ground clearance to be varied, the ability to quickly change the engine in the field, the American 152 mm gun/launcher M170 (with an autoloader in the rear of the turret), and more.

The most notable things, though, other than the gun/launcher, were first of all that the driver was located in the turret rather than the hull. His station was at the left front, with a cupola that automatically rotated in the opposite direction of the turret so he always faced forward, and had three large periscopes for vision. In case of damage to one, they could be quickly swapped around, and if that wasn't possible, the cupola could also be switched to always have one of the two side periscopes face forward instead. The reason to put the driver in the turret is often misrepresented: the real one was due to the required NBC protection, which was to include a thick polyethylene liner to shield against neutron bombs. By putting the driver in with as the rest of the crew, only one compartment needed to be shielded rather than two. The drawing below shows the prototypes' armour thicknesses, with the grey lines being the polyethylene anti-radiation shielding:

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The second most notable feature was the anti-aircraft armament. Rather than putting a machine gun on the commander's hatch, the vehicle had a complete remote-control turret with a 20 mm Rh 202 cannon and dual ammunition feed, aimed and fired entirely from under armour by the commander from his station. The gun folded out of the way when not needed, with its barrel pointing rearward along the left side of the turret roof and armoured shields covering the subturret's open top.

Differences between the German and American tanks were mostly the engine, as mentioned; this lead to different engine decks and hull rears to accommodate them. The American tanks can be easily recognised by the engine deck having two row of grilles on the front engine deck, below the turret bustle, and a simple flap covering a wide opening in the hull rear. The German tanks, on the other hand, have two circular air intakes on the rear of the engine deck, behind the turret, and a large grille in the rear plate. Other differences are in the smoke launchers (four each side on American tanks, eight on German) and the front and rear lights and other minor fittings.

Though testing revealed a number of teething problems, this was not unexpected, of course, and by the early 70s, the tank was ready for production. In the US Army, it was adopted as the 152-mm Gun Tank M70, officially nicknamed Krueger after the German-American general (though nobody seems to have realised he had a namesake that makes this slightly awkward). In the German Bundeswehr, it became known as the Kampfpanzer Keiler ("Wild Boar"). From here, though, both countries' vehicles soon began to diverge as each started improvement programmes that weren't really synchronised very well.

In the 1960s, the British had developed Chobham armour, that offered markedly better protection against shaped charges than the spaced armour the M70 had been developed with, and soon shared its secret with the Americans. This soon lead to the turret design being improved to incorporate this new armour, discarding its previous curved shape because Chobham-type armour cannot be made round. Instead, a turret with flat, sloping front plates and a new, angular mantlet were installed, as well as deep side skirts over the suspension. At the same time, the 20-mm gun was replaced by a .50-caliber M85 machine gun, the Americans never really having liked the gun forced on them by the Germans in return for accepting the 152-mm gun/launcher. The Germans meanwhile upgraded their Keilers by removing that same gun/launcher and replacing it by a new Rheinmetall 120 mm smoothbore gun, still fed by an autoloader but with increased capacity due to the smaller rounds, as well as improving the armour while keeping its original shape. Both these versions came into service in the late 1970s, almost at the same time.

By the early 1980s, though, the US Army was starting to tire of the 152 mm gun/launcher it had expected so much of. In all three vehicles fitted with it (M551, M60A2 and M70), it proved very troublesome in all manner of ways, leading to the early retirement of the M60A2 and the removal of M551s from most units except ones that actually needed its light weight (mainly airborne ones). The German 120 mm gun looked like a good solution for the M70, so after some redesign of both gun and tank, it was adopted in 1983 as the M256 gun, being installed in an M70A1 turret that had been further improved. The main change, other than the autoloader and other internal changes, was to install blast panels in the roof over the autoloader, so that an ammunition explosion would be vented upwards away from the crew. This was standardised as the M70A2 in 1984 and began to be delivered to front-line units in Germany soon, replacing original M70s first, followed by M70A1s that were sent back to the USA to be reworked to the latest configuration.

In this guise, the M70 took part in Operations Desert Shield and Desert Storm, following the Iraqi invasion of Kuwait in August 1990. It proved to be an outstanding tank in its first actual combat deployment, silencing most of its remaining detractors with its mobility, firepower and armour protection.

[Old Wombat]

How did they manage to get past the drivers becoming so disorientated that many of them threw up after only a very short time driving the vehicle?

[Jakko]

They installed a rack for ten examples of the Bag, Sick, M180A2 on the left side of the the driver's module. This is one area where the American version was more advanced than the German one, in which the Dutch Army's drivers had to make do with empty frietzakjes.

[Jakko]

And on to the model About four years ago, on another forum there was going to be a "what-if" group armour build, and I thought an updated MBT 70 would be fun. Unfortunately it turned out that the person running the GB had very much "Wehrmacht 1946", or at least "Second World War unbuilt prototypes", in mind and wouldn't allow anything post-war. Didn't stop me from buying a Dragon KPz 70 kit and upgrading it, though:

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Though it says "MBT-70 (KPz. 70)" on the box, the model is very definitely the latter and not the former (BTW, I tend to use MBT 70 to refer to the American tank and KPz 70 for the German one), but my idea was an American tank in the Gulf War, so I now had great fun trying to work out what to change to turn the model in that. My main reference for this was Hunnicutt's Abrams: A History of the American Main Battle Tank, which doesn't just cover the M1 Abrams but also the MBT 70 and XM803 that went before it.

Because of the different engine, I needed to remove the whole engine deck from the upper hull:

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After puttying shut the grille on the side, I closed the hole at the front of the engine deck, recessing that a little compared to the rest of the deck (by simply glueing it to the underside of the deck plates), and put an I-beam in across to give it some strength:

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After that I cut pieces of plastic card and mesh from an old kit (the type supplied to put mesh into stowage racks and things):

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This all makes a sandwich of stuff to recreate the intake grilles:

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The rear part of the engine deck is wider because ... well, if I'm honest, because I didn't realise the difference here was due to early vs. late prototypes. Early prototypes had snorkels along the sides of the engine deck, under long, narrow hatches, but these were deleted later and the sides of the engine compartment were sloped instead. So the M70A2 still has those, maybe the spaces were retained for stowage?

In any case, the next step was:

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... to cut all of that back out again I suddenly remembered that I also own a copy of Spielberger's Waffensysteme Leopard 1 und Leopard 2 and wondered if that covers the KPz 70 too. Turns out it does, and it includes what appears to be scale drawings of the American version — which showed that 1) my measurements in the drawings in Hunnicutt's book were off, 2) the forward removable part of the engine deck was wider on the  American tank than on the German one, and 3) my assumption about the direction of the mesh was wrong too (I had made it diagonal, turns out it was square). Let's do it all again!

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With a different mesh, but also more accurate dimensions. In the photo above I've also added plastic strip for the frames around the mesh, as well as more detail to the engine deck.

[Wardukw]

This is going to be good I can tell   

What are ya going to do with the main gun mate?
Going to upgrade to the M256 120mm ?

[Gondor]

Oh I like this   

Gondor

[kerick]

This is really cool! Looks like the whole front of the turret gets rebuilt too. Then you have a big fat 152mm gun barrel to play with.

[Old Wombat]

Going to upgrade to the M256 120mm ?

I'm guessing a Rheinmetall Rh-120 L/44, as per the Leo 2.

(Mostly a terminology difference but I'm sure the US manufactured gun differs from the German version somewhere along the line.)


Excellent work on the build, so far, Jakko!

[kerick]

BTW, your scratch-fu is very strong! 

[Wardukw]

Going to upgrade to the M256 120mm ?

I'm guessing a Rheinmetall Rh-120 L/44, as per the Leo 2.

(Mostly a terminology difference but I'm sure the US manufactured gun differs from the German version somewhere along the line.)


Excellent work on the build, so far, Jakko!

Guy there the same gun ..M256 is just the US designation for the Rh-120 L44.
I do wonder if at some point the US will install the L55 gun into a Abrams..it's quite a bit more powerful than the L44 .
The Leo 2A6 and 7 both use the L55 and they are extremely lethal tank guns.

[Old Wombat]

Going to upgrade to the M256 120mm ?

I'm guessing a Rheinmetall Rh-120 L/44, as per the Leo 2.

(Mostly a terminology difference but I'm sure the US manufactured gun differs from the German version somewhere along the line.)


Excellent work on the build, so far, Jakko!

Guy there the same gun ..M256 is just the US designation for the Rh-120 L44.
I do wonder if at some point the US will install the L55 gun into a Abrams..it's quite a bit more powerful than the L44 .
The Leo 2A6 and 7 both use the L55 and they are extremely lethal tank guns.

Technically the same, but the US tends to use their own manufacturing techniques, fixings, bolts, etc., & these tend to mean that parts for the US M256 won't, necessarily, be interchangeable with those of Rheinmetall guns.

L/44 or L/55 would depend on whether Jakko was building an early or late version of the KPz 70 - A point which has just made me realise that he's building the US MBT 70 which makes the whole Rheinmetall thing moot. (Oops! )

[rickshaw]

An example of how the US differs from European manufacturing is the use of alternative fasteners, screws and bolts and nuts and so on.  The Merlin engine in WWII was given to Ford for them to license produce it and they decided to use American fasteners in it's redesign.  The result was that the engine ended up substantially different.  So different that you could not mix the two.  US manufactured engines were almost completely different to British produced or even Canadian produced versions.  This was repeated in the famous Vickers 105mm L7 gun.  The British used one version and the Americans another.  The most obvious difference was the fume extractor.  The British version was symmetrical, the American version was not.  The two guns are not interchangeable.  There are, I don't doubt other examples but they are the two that immediately spring to mind.   

[buzzbomb]

Yippeee... really like what I see already

[NARSES2]

Very neat work sir 

[Wardukw]

Going to upgrade to the M256 120mm ?

I'm guessing a Rheinmetall Rh-120 L/44, as per the Leo 2.

(Mostly a terminology difference but I'm sure the US manufactured gun differs from the German version somewhere along the line.)


Excellent work on the build, so far, Jakko!

Guy there the same gun ..M256 is just the US designation for the Rh-120 L44.
I do wonder if at some point the US will install the L55 gun into a Abrams..it's quite a bit more powerful than the L44 .
The Leo 2A6 and 7 both use the L55 and they are extremely lethal tank guns.

Technically the same, but the US tends to use their own manufacturing techniques, fixings, bolts, etc., & these tend to mean that parts for the US M256 won't, necessarily, be interchangeable with those of Rheinmetall guns.

L/44 or L/55 would depend on whether Jakko was building an early or late version of the KPz 70 - A point which has just made me realise that he's building the US MBT 70 which makes the whole Rheinmetall thing moot. (Oops! )

Hahaha ..the real main differences would be you'd think be the measurements but the military run in metres and millimeters .
The Rh120 is made in the metric world and so is the US one..keeps the manufacturing simple..have ya noticed that apart from  50cal ..which is 12.7mm and .45 ACP everything else is metric..5.56..7.62..9mm.
They call the gun the M256 120mm not the M256 4.72in.
Yeah I know it's weird how the USA live with feet and inches but the military have been using metric since just before the Vietnam War.
Watch enough Vietnam War movies and you'll hear something is half a click down the road at some point 😀