Why are modern tank cannons of the 120 mm caliber

Discussion in 'History' started by fedr808, Aug 19, 2011.

  1. fedr808 1100101 Valued Senior Member

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    I know that there is some slight variation to this, a few tanks with 125 mm cannons.

    But why are most tanks sticking with 120 mm? Is it the ideal caliber between penetration, damage, and reload time?
     
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  3. cosmictraveler Be kind to yourself always. Valued Senior Member

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    Perhaps because they can be used by many countries. If only one country bought this then there could be many other types as well which could be a problem in manufacturing so many varied sizes for so many countries. I think that NATO also asks for a single type to use with its partners.:shrug:
     
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  5. fedr808 1100101 Valued Senior Member

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    Maybe
     
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  7. Cifo Day destroys the night, Registered Senior Member

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    There's the practical restrictions on the size of tanks, such as fitting then into transport aircraft and onto railway cars, as well as weight restrictions of bridges, all of which would reduce their practical military value.

    Of the tank itself, there's physical considerations such as the weight and length of the gun and the number of on-board rounds, which requires making the tank more massive, along with a more massive engine and fuel tank to move it (and more/larger refueling vehicles along with their increased fuel consumption and crews), or restricting the caliber and/or the number of on-board rounds, or limiting its time in battle (ie, requiring it to return more often for refueling and reloading).

    Also, if the autoloader becomes disabled, the crew can only safely handle a certain size/weight round.
     
  8. KilljoyKlown Whatever Valued Senior Member

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    Apparently they did try a 140mm gun for awhile.

    For more Info. http://en.wikipedia.org/wiki/Rheinmetall_120_mm_gun
     
  9. Robert Schunk Registered Senior Member

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    104
    I'm not all that familiar with tank guns, but I am massively familiar with naval artillery and coast artillery, and I'm aware that the Yamato-class BB's couldn't fire their 18-inch main batteries without damaging their own superstructures due to the immense sound pressure created by their propellant charges.

    Knowing this, I like KillJoyKlown's explanation:

    "The Rheinmetall 120 mm gun is a smoothbore tank gun designed and produced by the West German Rheinmetall-DeTec AG company, developed in response to Soviet advances in armor technology and development of new armored threats. Production began in 1974, with the first version of the gun, known as the L/44 as it was 44 calibers long, used on the German Leopard 2 tank and soon produced under license for the American M1A1 Abrams and other tanks. The American version, the M256, uses a coil spring recoil system instead of a hydraulic system.[3] The gun has also been exported to South Korea and Japan for their indigenous tank designs, as well as other nations that have procured the Leopard 2 and the M1 Abrams. The 120-millimeter (4.7 in) gun has a length of 5.28 meters (17.3 ft), and the gun system weighs approximately 3,317 kilograms (7,310 lb)."

    "By 1990 the L/44 was not considered powerful enough to deal with the latest Soviet armor such as the T-80B, which stimulated an effort by Rheinmetall to develop a better main armament. This first revolved around a 140-millimeter (5.5 in) tank gun named Neue Panzerkanone 140 ("new tank gun 140"), but later turned into a compromise which led to the development of an advanced 120 mm gun, the L/55, based on the same internal geometry as the L/44 and installed in the same breech and mount. The L/55 is 1.3 meters (4.3 ft) longer, giving an increased muzzle velocity to ammunition fired through it. As the L/55 retains the same barrel geometry, it can fire the same ammunition as the L/44."

    "This gun was retrofitted into German and Dutch Leopard 2s, and chosen as the main gun of the Spanish Leopard 2E, the Greek Leopard 2HEL, and new South Korean K2 main battle tank. It has been tested on the British Challenger 2 as a potential replacement for its current weapon, the rifled L30 120 mm cannon."

    "A variety of ammunition has been developed for use by tanks with guns based on Rheinmetall's original L/44 design. This includes a series of kinetic energy penetrators, such as the American M829 series, and chemical energy anti-tank warheads. Recent ammunition includes a wide range of new anti-personnel rounds and demolition munitions, giving tanks armed with the L/44 and its derivatives greater versatility on the modern battlefield. The LAHAT, developed in Israel, is a gun-launched missile which has received interest from Germany and other Leopard 2 users, and is designed to defeat both land armor and combat helicopters. The Israelis also introduced a new anti-personnel munition which limits collateral damage by controlling the fragmentation of the projectile."

    ***

    Plus, one fact which even KilljoyKlown's overlooked:

    The 120mm/125mm guns are SMOOTHBORES!!!!!, capable of taking APFSDS rounds (i.e., no rifling needed, as the shells themselves contain their own spin).

    Big bore (just like me!!!), no rifling to slow the projectile down (as the projectile contains its own spin, expressed after fin deployment following sabot discard (i.e., after clearing the muzzle )), and freedom from the logistical problems inherent in loading too few shells of excessively large calibre, the 120mm/125mm smoothbore seems, to me, the way to go.
     
  10. KilljoyKlown Whatever Valued Senior Member

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    I was wondering about that, thanks. Having all tanks use the same size round makes very good logistical sense, and 120mm seems to be as big as anybody wanted to handle, and you can make a large variety of rounds at that size.
     
  11. fedr808 1100101 Valued Senior Member

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    Okay, thanks guys
     
  12. Sock puppet path GRRRRRRRRRRRR Valued Senior Member

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    I would just add that 120mm was where nato was, 125mm for the soviets/warsaw pact, when the cold war arms race ended. No non nato country has made anything significantly better armoured in the last couple of decades so the 120mm L/55 can still easily deal with all threats at standoff range. Should some new beast pop up that is able to defeat the 120 we will no doubt see a new tank gun.

    Echo should be on this thread
     
  13. fedr808 1100101 Valued Senior Member

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    Thanks
     
  14. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    Really? As your own source states:
    MOST 120/ 125mm weapons are smoothbore.

    Arrant nonsense.
    APFSDS rounds (and they are shot, not shells) do not spin.

    Also wrong. The fins do not "deploy" they are an integral, fixed, part of the round.

    You really should try to avoid posting on subjects of which you apparently know nothing.
     
    Last edited: Aug 22, 2011
  15. AnWulf Registered Member

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    9
    As a former tanker, I can tell you that you want a round big enough to do the job but the bigger the round, the fewer you can carry. Going to the 120 from the 105 lowered the tale of rounds we could carry on the tank.

    One of the problems tankers had during the Gulf War was that the sabot rounds were going right thru the Iraqi tanks. Tankers developed a habit doing a double tap ... a sabot round followed by HEAT round.
     
  16. KilljoyKlown Whatever Valued Senior Member

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    Can you please describe how that double tap works? If the first round goes through the tank, I would think it's a done deal. What's the point of a second heat round?
     
  17. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    If it goes through it may or may not have done any real damage (unlikely, but possible).
    The second round will most probably ignite the target - a burning tank can be considered definitely out of a fight, whereas a merely stationary one may just be playing possum.
     
  18. KilljoyKlown Whatever Valued Senior Member

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    AnWulf can you talk about how and why these rounds are used. Thanks

    Kinetic Tank Rounds

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    Heat M380 Round

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    Depleted Uranium Anti-tank Round

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  19. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    How strange.
    A full-calibre DU round.
    Looks like someone wasted their time...
     
  20. KilljoyKlown Whatever Valued Senior Member

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    Were you expecting one that looked like this?

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  21. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    Not quite: more like the APFSDS (kinetic rounds) in your first photo.

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  22. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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  23. Believe Happy medium Valued Senior Member

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    Yeah I'm confused about this as well. It was my understanding (and I could be wrong here) that a sabot was SUPPOSED to go through the tank and come out of the other side. This was supposed to be done with so much force that it sucks the crew out of the tiny hole on the other side, or at least completely ruins their day (i.e. popped eardrums for everyone) . (again when I think about this it sounds like BS but this is what I was told by tankers so.....idk)
     

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