Studies on 140mm Tank Guns

[MKSheppard]

United States

The 140mm smoothbore Advanced Tank Cannon (ATAC) System consists of the XM291 gun, the XM91 autoloading system and a family of 140mm ammunition.

The ATAC System was expected to be the main armament of the US Army's future Block III MBT, a key part of the projected Armored Systems Modernisation.

The ATACS is being installed in the Component Advanced Technology Test-Bed (CATT-B). This is based on an M1A1 Abrams chassis and, in addition to the ATAC System, has Advanced Integrated Propulsion System (AIPS), hydropneumatic suspension, Standard Army Vetronics Architecture, Rockwell Multi-sensor Target Acquisition Sensor, CDC ADA based fire control system, lightweight track, modular armour, advanced chemical agent alarm, NBC collective protection system and a Vehicle Integrated Defense System with countermeasures, threat sensors and smoke.

Prior to being installed in the CATT-B, the ATAC System has been installed in a modified M1 turret on a standard M1 chassis. This also features the Benet Laboratory designed automatic loader, modified M1A1 fire control electronics, Rockwell Multi-sensor Target Acquisition Sensor (qv), standard M1 gunner's primary sight and a new fire control computer. In this vehicle the gunner is on the right, as in the M1, while the tank commander is on the left in the space normally occupied by the loader.

The XM291 gun is a solid propellant tank gun with an integral mount and recoil mechanism that fires two-piece (projectile and charge) ammunition with twice the muzzle energy of the standard 120mm M256 gun installed in the current M1A1 and M1A2 Abrams MBTs. The ordnance is fitted with a thermal sleeve, fume extractor and is 91 kg lighter than the standard 120 mm M256 ordnance.

By means of a simple tube change, which takes one hour to accomplish, the system can also fire 120 mm one-piece conventional and advanced ammunition.

During operation of the XM91 autoloading system, developed by the US Army's Benet Laboratory, the selected ammunition type is identified, the telescoped cell containing that cartridge is moved to the loading port and the loading door is opened. The rammer mechanism then moves forward and grasps the rim of the stub base, the round gripper mechanism which holds the cartridge in place is released and the inner cell moves forward.

Docking of the inner cell with the breech occurs on full extension and the round is seated in the gun. The ram head and the inner cell then retract to their original position and the loading door is closed. The downloading sequence is similar and an ammunition re-arm port is provided at the rear of the autoloader for that procedure.

The ammunition transfer mechanism has been developed by Martin Marietta with the ready use bustle-mounted magazine holding 17 120mm or 140mm rounds, with the hull magazine holding 22 140 mm two-piece rounds as components or 33 single-piece 120 mm rounds.

Automatic loading takes place at the rate of 8 to 12 rds/min, with the rammer being provided by Brunswick Defense (qv).

The ATAC System family of ammunition consists of three cartridges: the XM964 kinetic energy (KE) cartridge; the XM965 chemical energy (CE) cartridge; and the XM966 training cartridge for both rounds.

Each cartridge consists of a forward and rear component. The rear component, which is identical to all three cartridges, consists of a stub base and primer assembly (similar to that of a standard 120mm cartridge), a combustible side wall, an ignition system and propellant.

The forward component houses the appropriate projectile, partially telescoped within the primary propelling charge, and propellant in a combustible cartridge case which also contains a relay charge at its base for the transfer of ignition from the rear component. A snap joint joins the two components allowing cartridge removal from the breech. The cartridges offer a muzzle energy that is double that of the standard 120mm system.

Switzerland

Switzerland has successfully carried out firing trials of a new Swiss designed and built 140mm smoothbore tank gun installed in a Leopard 2 MBT of the Swiss Army.

Switzerland has a total of 380 Leopard 2 MBTs designated the Panzer 87 (Pz 87 Leo), of these 380, 35 came direct from Krauss-Maffei of Munich and the remainder were manufactured under licence by Swiss industry with final deliveries being made in 1993.

The Leopard 2 is armed with a German Rheinmetall 120mm smoothbore gun which fires two types of ammunition, Kinetic Energy (KE) Armour-Piercing Fin-Stabilised Discarding Sabot - Tracer (APFSDS-T) and Chemical Energy (CE) High Explosive Anti-Tank Multipurpose Tracer (HEAT-MP-T). Both of these ammunition types have a semi-combustible cartridge case and all that remains after firing is the short case stub.

In the late 1980s, k + w Thun (Swiss Federal Armament Works Thun) started a development programme to demonstrate the feasibility of a more powerful gun, not only to upgrade the Leopard 2 but also to be used as a fortress weapon.

At the same time, the weapon was to be used to prove the anticipated performance of the ammunition and to integrate the gun and its associated ammunition into existing MBTs with minimal costs being involved.

The experimental ammunition for the 140mm smoothbore tank gun was developed by the Swiss federal ammunition factories in co-operation with partners of other nations.

First ballistic verification of the Swiss 140mm smoothbore gun under live conditions took place in the Summer of 1988 with the first projectiles being fired from the weapon installed in a Leopard 2 MBT taking place in the Autumn of 1989.

To ease handling, the ammunition is in two parts. The main propellant charge has a steel bottom and a combustible container with about 10 kg of propellant, and one part with either a KE projectile plus an additional 5 kg of propellant or a Multipurpose (MP) round which would probably not require the additional charge. The propellant will be optimised for the KE projectiles.

The KE projectile has a long rod penetrator of conventional material, not depleted uranium as used in US projectiles of this type, and a sabot with a plastic driving band. The first experimental MP round is a shaped charge with an additional strong fragmentation effect.

The chamber of the Swiss 140 mm smoothbore gun is somewhat shorter than the NATO layout but in order to keep the volume within the present international trend it has a larger diameter.

According to k + w Thun, its 140 mm smoothbore gun and projectiles can be adapted within a short space of time, if required to do so by international standardisation of the chamber.

Development efforts on the ammunition side have been concentrated on analysis of the terminal ballistics of KE projectiles with various designs (length, diameter, weight and velocity) against several types of test target. At the same time, the effect of the MP rounds was also investigated in static tests.

Trials so far have shown that both types of ammunition will penetrate around 1,000 mm of steel armour, which is a significant increase in penetration over current in-service 120 mm projectiles.

It is stressed that the Swiss 140 mm smoothbore gun is at present a research gun and has not yet been fully developed, and given the reduced threat since the weapon was conceived, it is not likely to be deployed in the near future.

Germany

Under contract to the BWB, Rheinmetall has built six prototypes of a 140mm smoothbore gun and its associated APFSDS-T ammunition for trials purposes.

This development contributes to the international Future Tank Main Armament (FTMA) programme, as defined in the quadrilateral MoU between France, Germany, UK and the USA.

The new 140mm smoothbore gun is called the NPzK-140 and is fitted with a vertical sliding breech mechanism, thermal sleeve and a fume extractor.

If the threat changed in the future, the German Army would have the option for a firepower improvement programme for the Leopard 2. The installation of a 140 mm gun would probably require the installation of a new turret fitted with an automatic loader to handle the separate loading 140 mm ammunition.

[KlavoHunter]

"In the late 1980s, k + w Thun (Swiss Federal Armament Works Thun) started a development programme to demonstrate the feasibility of a more powerful gun, not only to upgrade the Leopard 2 but also to be used as a fortress weapon. "


Do the Swiss seriously still have static fortifications as major defenses, in the day of the laser-guided bomb?

[Sidewinder]

The mention of combustible propellant casings reminds me of a problem the US Army's 152 mm gun/missile launcher had; that its casing would sometimes fail to vaporize completely, forming a puddle of molten plastic at the bottom of the gun breech, which could make the next round to cook off (fire before the gunner pulls the trigger). I wonder if they managed to solve the problem by the time the article was written?

Do the Swiss seriously still have static fortifications as major defenses, in the day of the laser-guided bomb?

I remember reading a 1980s issue of National Geographic, which had an article on Switzerland and described some details of their fortresses (it even had a picture of a heavy mortar whose mount is disguised as a tree stump). A Swiss officer was quoted as saying, "As long as the mountain fortresses hold, Switzerland will never fall," or something to that effect. I don't know whether or not these mountain fortresses (the locations of which were state secrets) are still being maintained.

[MKSheppard]

I wonder if they managed to solve the problem by the time the article was written?

Uh yes; the propellant cases on the M1A1's 120mm are combustible walled with a brass base case.

[Sea Skimmer]

Do the Swiss seriously still have static fortifications as major defenses, in the day of the laser-guided bomb?

Laser guided bombs are not an overwhelming threat to a modern fixed fortification, laser detectors can be used to automatically trigger water curtains or smoke generating system which fuck up the laser beam and makes the bomb go dumb. The Swedes used such system extensively to protect coastal batteries, I can only assume Switzerland made similar upgrades. Anyway, the main threat was Soviets and the Soviets were not in the business of using laser guided bombs (which few 1980s aircraft actually carried, even in NATO) for close air support as is done so often today. Its only after the Cold War that the effects of the PGM revolution of tactical air support have matured.

Most Swiss fortifications have at last been decommissioned in the last 10 years, but they had a very massive network of them defending a huge Alpine redoubt (forts on top of and tunnels through the insides of 10,000ft mountains are not easily taken) the origins of which dated back to before WW1. Besides this redoubt they had numerous delaying lines throughout the lowlands and valleys to grind up an invader before he could even begin to attack the redoubt area. Even for a 2008 army with GPS guided everything it would have been one hell of a bitch of a place to assault, after all you can’t use precision guided weapons until you have a precision target. Most of the time, you’d only have that target after a set of defense had already opened up in an ambush, inflicting heavy losses on any mechanized force trying advance up narrow Alpine roads and valleys.

BTW, by 1989 the Swiss had blast protected nuclear shelters (not mere fallout shelters) for 97% of the population, with every new building being required to have a shelter not only capable of accommodating its occupants but also a margin of people from off the streets, caught in a surprise attack. The plan was to reach 100% capacity by 2000, but the end of the Cold War scaled back building plans, though IIRC the shelters were still required for new buildings until very recently.

[Shroom Man 777]

BTW, by 1989 the Swiss had blast protected nuclear shelters (not mere fallout shelters) for 97% of the population, with every new building being required to have a shelter not only capable of accommodating its occupants but also a margin of people from off the streets, caught in a surprise attack. The plan was to reach 100% capacity by 2000, but the end of the Cold War scaled back building plans, though IIRC the shelters were still required for new buildings until very recently.

Holy hell. How did the Swiss pay for that? That must've been... expensive.

[TheMuffinKing]

BTW, by 1989 the Swiss had blast protected nuclear shelters (not mere fallout shelters) for 97% of the population, with every new building being required to have a shelter not only capable of accommodating its occupants but also a margin of people from off the streets, caught in a surprise attack. The plan was to reach 100% capacity by 2000, but the end of the Cold War scaled back building plans, though IIRC the shelters were still required for new buildings until very recently.

Holy hell. How did the Swiss pay for that? That must've been... expensive.

Nazi gold?

[KlavoHunter]

Holy hell. How did the Swiss pay for that? That must've been... expensive.

Nazi gold.


e:f,b


It helps to have all the world's money being stored in your bank accounts.

[[R_H]]

If anyone wants, I could take some pictures of the shelter in the basement of the apartment building I live in and post them in this thread.

[KlavoHunter]

If anyone wants, I could take some pictures of the shelter in the basement of the apartment building I live in and post them in this thread.

Are you kidding? Of COURSE we want to see that!

[[R_H]]

If anyone wants, I could take some pictures of the shelter in the basement of the apartment building I live in and post them in this thread.

Are you kidding? Of COURSE we want to see that!

Alrighty then, I'll go snap some pictures.

[[R_H]]

OK, here are the pics.


The door itself. Concrete with a steel frame.



Coming into the basement. The blast shelter is off to the left, and also doubles as storage for each of the tenants (partionned off with the wood planks as seen in this picture to the right, just before the door.



Thickness of the door, about 20cm.



Inside of the door. There are two dogs, and the screw/bolt (don't know what the appropriate term for it would be) in the middle is used to somewhat seal the shelter off.



The inside of the shelter, which, as previously stated also doubles as storage for tenants. Inside the partion closest to the door there's an escape hatch that goes somewhere. It's buried behind all our boxes, but I'll try to get a shot of it.