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Modern MBT Question

Discussion in 'Post-World War 2 Armour' started by Boba Nette, Jun 19, 2005.

  1. Grieg

    Grieg New Member

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    gp wrote:

    Wrong. HESH rounds don't enter anywhere. They are designed to create spalling without penetrating the armor. It is acknowledged that they are generally ineffective against spaced armor, laminated, composite armor and some types of ERA armor.

    Spalling is caused by a shockwave passing through the armor plate and breaking off pieces of the inside plate which can be propelled with considerable force. Other pieces inside the tank may be jarred loose but since the shockwave isn't propelling them directly it is doubtful that they would cause significant damage. Of course, considering the nature of the Abrams armor the HESH round wouldn't likely transfer enough force to the inside to cause either spalling or to jar loose equipment. Simple spaced armor will defeat the HESH round much less composite armor.


    Wrong. At the velocities and range we are dealing with the trajectory cannot possibly approach the parabolic curve you describe. The trajectory at 1400 meters is nearly flat, within a few degrees of horizontal.
    To calculate the trajectory you only need the ballistic coefficiency of the round and the velocity. Even though the HESH round trajectory isn't as flat as the extremely flat KE round round trajectory (>1600m/s) it is still relatively flat. I don't intend to tackle the math to settle this dispute because it is silly to even contemplate. With even the most basic knowledge of external ballistics the idea of striking near vertical from 1400 meters and at velocites greater than 1000 meters per second is ludicrous. One would need to aim nearly vertical such as with a mortar (with much lower velocites) and the main gun isn't even capable of elevating to near vertical positions.

    It doesn't use Chobham armor, strictly speaking. The armor is very similar in that it is a laminated,composite material , that uses ceramics imbedded in a matrix of other classified material. The Abrams also has steel encased DU.
    It's not too hard to understand. The Challanger and the Abrams' armor are quite similar in many respects yet different in some other ways.




    So do mine but the difference is that they aren't "war stories" or anecdotes of dubious veracity but are taken from published reports by the people who developed the weapons systems as well as those who use them. You made a similar claim about the erroneous statements you made regarding the altitude of A-10 attack profiles in the Gulf War until proven wrong.
     
  2. Ricky

    Ricky New Member

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    Sorry, I just can't stop myself!

    I think GP was referring to a different thread (or was it earlier in this thread) when you stated that the M! series does not have chobham-type but developed chobham... :wink:
     
  3. Grieg

    Grieg New Member

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    gp wrote:

    I stated in my previous posts on the subject that some of these capabilities were present in other allied forces, just to a lesser extent and lacking the all important Command and Control systems(FBCB2..Force XXI etc ) that allows these capabilities to be exploited to their fullest extent.


    This is not the first time you have launched a childish personal attack in your posts addressing me. I'm mystified as to why repeat behavior of this type is tolerated.

    ps If the problem is only with me what does " the bragging of the US military whiles others do the job. " statement mean?
     
  4. Grieg

    Grieg New Member

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    ricky wrote:

    But you miss the point. The issue at hand is not whether such a thing could happen. Clearly it did. The issue was whether or not the storage of main gun ammo in the crew compartment was a potential weakness of the Challenger. Only the hatch being open allowed the HESH round to enter the turret and the secondary explosion destroyed the tank and killed the crew. The round striking the open hatch while travelling horizontally is a fluke. In contrast to what GP was saying the HESH round was travelling horizontally when it struck the hatch i.e. a flat trajectory.
    GP was claiming that HESH rounds are normally fired at such a trajectory as to strike the top of the tank which is preposterous.
    Getting back to the issue at hand it becomes clear that if anything enters the turret that can ignite the main rounds then you have a catastrophic loss. The Abrams that had the turret (turret well...which is actually the hull...no composite armor such as on the turret has been penetrated yet by hostile fire AFAIK) penetrated was a case in point that insignificant damage can result from a small penetration which contradicted GPs statement that it doesn't matter since if the turret is penetrated the crew is just as dead.


    They could at extreme ranges. If you calculate the ranges based on the velocity you will find that they are outside any normal combat ranges. It happened once in the Gulf War at extreme range but even in that case AFAIK the HESH round did not impact the top surface. The targeting and fire control system not to mention the armor doctrine used does not contemplate normally engaging targets at such extreme ranges.
    To attempt it at shorter ranges isn't possible because the main gun cannot elevate to a near vertical position.

    I was. He was. He was also mischaracterizing my statements. I well know that Abrams armor initially was developed directly from Chobham armor. Since then significant changes have been made while retaining some of the same characteristics, as I stated earlier.
    Where have I contradicted myself?
     
  5. Ricky

    Ricky New Member

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    Um, in this case, in the thread 'Does Chobham Armour resist multiple hits' you can find the following post:

    And then here you say:

    :wink:

    But this is just being picky. :p


    Did you miss my post? GP has been warned.

    Please do not respond with anything resembling a personal remark - we do not like having to lock topics and rap knuckles. :wink:
     
  6. Grieg

    Grieg New Member

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    ricky wrote:

    .

    It depends upon what the defintion of "is" is :grin:
    One has to put these quotes into proper context. The issue being discussed in those posts was slightly different.
    It would be accurate to say that the composite portion of the Abrams armor is chobham type armor. I mentioned earlier what that means. Ceramic plates imbedded in a matrix of a "cement". However that is only a portion of the armor. It doesn't include the steel encased DU. So while it is correct to say that the Abrams amor incorporates chobham type armor it would not be correct to state that the Abrams "uses Chobham type armor" unless it is specified what it uses in addition to that composite armor. It uses Chobham type armor yes but not exclusively so that isn't the whole story thus the statement is misleading.

    In the context of the statement here it doesn't matter because the fact remains that HESH rounds aren't effective against Chobham armor, Chobham type armor or Abrams armor which is part Chobham type composite armor and part steel encased DU.
    In regard to the point being made it simply doesn't matter. It is an attempt IMO to obscure the real point.

    Yep. See above comments.

    I was responding to a personal remark rather than with one IMO.
    I didn't miss your post but hasn't a warning has been issued previously to the same poster for the same thing... and it was ignored?
     
  7. GP

    GP New Member

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    This is not the first time you have launched a childish personal attack in your posts addressing me. I'm mystified as to why repeat behavior of this type is tolerated.

    ps If the problem is only with me what does " the bragging of the US military whiles others do the job. " statement mean?[/quote


    do you know what the British army have then. please tell what kit i work with?
     
  8. GP

    GP New Member

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    It means that the US bragg about their capabilities, while other armies just get on with the job.

    As for attacks on you, it is because you are a person who only sees what you want to.

    You still haven't as for as I have seen answered some of my questions, such as why you still think Boeing use DU.

    You can if you wish pm me with an answer and say posting here.
     
  9. GP

    GP New Member

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    Edited by Moderator
    I did point out that the tank must raise it’s front. This can be easily achieved by driving up a hill or raised area of ground.

    It doesn’t need to be near vertical for a shot at distance, however, I realise you were wrongly talking about the near shot.

    By the way the velocity of HESH is more like 670 m/s not greater than your facts.

    See

    http://www.janes.com/defence/news/jdw/j ... _1_n.shtml

    Yes I corrected my self after you pointed out my mistake. Then I was explaining that at longer ranges and pointed out by Ricky.

    The challenger does not need a separate compartment as it is the most protected tank in the world. To this end no other nations tank ammo will set off the HESH rounds, except for British friendly fire (in this case they are dead anyway). This means they can put more ammo in the tank to fire.
     
  10. Grieg

    Grieg New Member

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    By the way the velocity of HESH is more like 670 m/s not greater than your facts. [/quote]

    Do you have a source for that muzzle velocity? It's difficult to imagine a modern main gun with such a low velocity. I wasn't wrongly discussing a near shot, I was talking about the range of the friendly fire engagement in question. For modern MBTs 1400 meters is not long range. However it desn't change anything, even if it were 670m/s which is close enough to the velocity of the German WW II era 88mm l/56 to give one an idea of how flat a trajectory we are dealing with, the 88mmwas considered to have a very flat trajectory, certainly nothing like a howitzer or mortar trajecetory such as would be necessary to impact horizontal surfaces.
    Can't you just picture all the Challengers scurrying about under fire trying to locate a suitable raised area high enough to enable them to return fire?
    How silly :wink:


    Your link is to a story about future UK Ranger battalions. I don't see the connection.


    The Aussies have been evaluating MBTs for their ADF. They chose the Abrams over the Challenger II and Leopard II.

    As far as the opinion stated that the Challanger is the best protected MBT in the world; that was a sentence in a paragraph about the Challanger II that has been copied many times with no attribution as to it's origin. It just someones opinion with no data or tests to support it. All of the major MBTs have classified armor about which very little is known publicly. They certainly don't publish the data regarding tests in unclassified sources.

    The 120mm Abrams main gun firing APFSDS would not likely have any difficulty in penetrating the Challenger II. (this is of course just opinion :wink: ) The UK apparently isn't satisfied with the 120mm L30 of the Challenger II either since they are planning on replacing it soon with a smoothbore similar to the German designed US gun which uses one piece ammo rather than the separate loads now used by the British gun.
     
  11. Oli

    Oli New Member

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    Several things:

    from Modeling of Tank Gun Accuracy under Two Different Zeroing Methods, David W, Webb RAND report at http://www.galaxy.gmu.edu/ACAS/ACAS00-0 ... bDavid.pdf

    It would appear that muzzle velocity is distinctly related to (propellant-formed) gas temperature: http://yarchive.net/space/exotic/gun_velocity.html and www.mines.edu/academic/mining/csm_isee/ ... f01_04.ppt
    Which would imply that a higher propellant temperaure is not simply to "consume the residue", it gives higher muzzle velocity for the same propellant mass, in fact propellant residue in any gun means wasted mass.
    Logically a higher combustion temperature (if true*, AFAIK all current tank gun propellants are much of a muchness), then surely a higher-temperature combustion would mean that the charges are less dangerous in that they require higher initial temperatures to ignite them.

    While I can't comment on German design philosophy for Leo 2, the British view is that ammo stored below the turret ring is less likely to suffer hits, and therefore doesn't need blow-out panels. But there's always the odd unlucky hit...

    Challenger 2 is switching to the Rheimetall 120 L/55 for, according to MoD sources, European ammunition commonality reasons (although there are rumours on the grapevine that CHARM2 isn't quite cutting it on barrel-wear considerations, but that's an, as yet, unconfirmed "insider" story).

    * The source quoted doesn't seem entirely reliable, since the Russian 125 mm gun is actually 2A46 (and variants) while the 2A25 designation given (in an aviation magazine?) was applied to an experimental 73 mm weapon (Lightning) for Ob'iekt 287 (similar to, but not the same as, 2A28 Grom on BMP-1). That and the seemingly nonsensical remarks about higher temperatures. For factors in the Australian choice check out -
    http://www.militaryphotos.net/forums/ar ... 15670.html
    http://www.minister.defence.gov.au/Hill ... entId=3643

    With regard to HESH possibly being top attack, for a typical modern day sized MBT the angle of descent for the round needs to be just under 46 degrees frontally (45.6) or 17.5 degrees on the side for the target to present equal areas (giving a 50/50 chance of a hit on top or side/ front).
    Highly unlikely for a front shot, even at long range, but possible at extreme range with a side-on shot, even if fired while the firing tank is horizontal since descent angle is usually greater than firing angle.
     
  12. GP

    GP New Member

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    Do you have a source for that muzzle velocity? It's difficult to imagine a modern main gun with such a low velocity. I wasn't wrongly discussing a near shot, I was talking about the range of the friendly fire engagement in question. For modern MBTs 1400 meters is not long range. However it desn't change anything, even if it were 670m/s which is close enough to the velocity of the German WW II era 88mm l/56 to give one an idea of how flat a trajectory we are dealing with, the 88mmwas considered to have a very flat trajectory, certainly nothing like a howitzer or mortar trajecetory such as would be necessary to impact horizontal surfaces.
    Can't you just picture all the Challengers scurrying about under fire trying to locate a suitable raised area high enough to enable them to return fire?
    How silly :wink:


    Your link is to a story about future UK Ranger battalions. I don't see the connection.


    The Aussies have been evaluating MBTs for their ADF. They chose the Abrams over the Challenger II and Leopard II.

    As far as the opinion stated that the Challanger is the best protected MBT in the world; that was a sentence in a paragraph about the Challanger II that has been copied many times with no attribution as to it's origin. It just someones opinion with no data or tests to support it. All of the major MBTs have classified armor about which very little is known publicly. They certainly don't publish the data regarding tests in unclassified sources.

    The 120mm Abrams main gun firing APFSDS would not likely have any difficulty in penetrating the Challenger II. (this is of course just opinion :wink: ) The UK apparently isn't satisfied with the 120mm L30 of the Challenger II either since they are planning on replacing it soon with a smoothbore similar to the German designed US gun which uses one piece ammo rather than the separate loads now used by the British gun.[/quote]

    http://www.janes.com/defence/news/jdw/j ... _4_n.shtml

    HESH L31 The HESH L31 is employed as a general purpose round with a good anti-armour performance as it is capable of defeating a NATO heavy single target at all ranges up to a maximum of 8,500 m; it can also be used in the indirect fire role. The projectile consists of a thin-walled projectile with a rounded ogive filled with 4.2 kg of RDX/Wax explosive detonated by a base percussion fuze. As with other projectiles of its nature, when the HESH L31 projectile strikes a target the thin walls collapse to allow the explosive to be spread over the surface of the target before the base fuze functions. The resultant detonation creates shock waves which force off a large high-velocity scab of material from the inner surface of the target armour. The latter capability makes the HESH L31 projectile effective against fortifications and structures as well as armoured targets. The HESH L31 is fired using the L3 bag charge containing 3.04 kg of NQ/S27-09 triple-base propellant. Muzzle velocity is 670 m/s.
     
  13. GP

    GP New Member

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    As for best protected tank, you claimed it was the Abrams. The rifled barrel they are happy with, it is just cheaper to use a standard NATO round, This is the reason for change.
     
  14. GP

    GP New Member

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    The HEP tests gave surprising results. One surprise, in addition to the target damage, was firing HEP at 1800 meters. The HEP round was quite slow (compared to HEAT and sabot), with a visible trajectory arc. We rarely fired practice HEP at over 1000 meters, because it was easy to miss, either over or short (these were M60A1 RISE Passive tanks, with old coincidence rangefinders and analog computers). I will say, though, that one of the prettiest main gun shots I ever saw was with practice HEP. We were training my driver as a gunner, and he was tracking a moving target at 1200 meters, with training HEP loaded. He was getting close to the range fan marker on the right, and I had just opened my mouth to command "cease fire," so the round wouldn't be fired outside the safety area, when he pulled the trigger. That HEP round sailed up into the air and down toward the target, and went through the middle of the turret, just a foot or two before it passed the range fan. TARGET!


    http://www.ciar.org/ttk/mbt/HESH-testfi ... kammo.html
     
  15. GP

    GP New Member

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    I will say again, the angle of impact is not as critical with HESH, as it doesn't hit then bounce off. It squashes the round prolonging the impact.


    The maths is not as easy to work out but anyone can see that if the impact is prolonged then there is less likelyhood of the round deflecting, even if it does the round is still close enough to have just as deadly effect as a square on hit.
     
  16. Grieg

    Grieg New Member

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    I've seen nothing to make me change that opinion.



    Maybe because the rifling results in lower muzzle velocities. To use a rifled barrel then use a fin stabilized penetrator that has a rotating band that prevents the round from spinning (because fin stabilization combined with rotating results in less accuracy) doesn't make much sense and muzzle velocities are said to be closer to 1500 m/s compared with 1700m/s plus for the smooth bore guns. Smoothbore guns are the state of the art.

    As far as HESH goes just because it hits the target doesn't mean it will function properly. If the angle is too great then the squashhead doesn't squash on the target but fragments. The first round in the friendly fire incident described apparently did just that when it hit the ground and fragmented, as noted in the report. No matter what anecdotes are told about how the trajectory looked (to tankers used to looking at the extremely flat APFSDS rounds) the external ballistics are more persuasive. What the eye sees is deceiving, the angle at which these rounds strike the target is only a few degrees from horizontal(except at extreme range) in reality.

    In any case it doesn't much matter since HESH is no good against anything but light armor or old iron armored targets without spaced or composite armor. It is likely that eventually the UK will drop the HESH rounds and go to something like the MPAT round which is an excellent all purpose HE round and is also useful against helicopters. Of course when they do I imagine that they will state that it was done for "European commonality reasons" :wink:
     
  17. Gryle

    Gryle New Member

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    I'd be careful about using the Australian purchase of M1s as an argument for their superiority, that particular decision was made without the usual army trials or tests and may well have been made for the current goverment's desire to be able to field some sort of expeditionary force capable of integrating well with US units and not with what the ADF actually needs.

    And where ever that quote comes from, it looks poorly researched. The AS1s are fitted with the L7A3 105mm, the M1s I believe have something like 3-6 rounds that aren't stored in the turret bustle (they are in a seperate blast vented compartment in the hull), some of the Leopard 2's ammunition is apparently protected in a similar fashion (just not the rounds stored in the hull) and the C2 I'm not familiar with , and the higher breech temps probably have more to do with being more modern guns firing at higher pressures and having semi-combustable cases than anything else.

    Still, the RAAC should be happy with any new vehicles they can get.
     
  18. Oli

    Oli New Member

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    Especially since (according to a report in Jane's Defence Weekly a couple of years back) some of the older Leopards in their inventory were degraded to the point of being vulnerable to 30 mm rounds in the frontal arc!
    Not good for an MBT.
     
  19. Grieg

    Grieg New Member

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    I posted the quote from Defence Today(August 2005) an apparently respected Aussie publication dealing with defense issues. Obviously I cannot vouch for accuracy of every word in the article. As far as the Russian 125m gun goes it could just be a typo. The T-64 and early T-72 variants had a 2A26(M2 IIRC) prior to the now standard 2A46.
    It seemed to me that the point was being made that the higher temperature propellants were necessary to entirely consume the combustible propellant cases used in the modern guns.

    I cannot say that the statement isn't true. Do you have specific knowledge regarding the burning temperature of modern propellants or the temperature necessary to consume the cases?

    Gryle wrote:

    The quote was to reinforce a point already made and IMO beyond dispute(and one which was apparently persuausive to the Aussies) i.e. placing the ammunition in separate armored compartments from the crew which are designed to blow out and away from the crew is a better and safer alternative to storing the ammo in the same compartment with the crew. Seems rather obvious to me.
    A good case could be made that the Challanger and crew destroyed in the friendly fire incident would have survived had not the ammo inside the crew compartment ignited.
     
  20. Oli

    Oli New Member

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    As far as I can ascertain gas temperatures run about 2290-3060 K, with the M30 propellant on the L7 105 (non-combustible case) at 3040 K, i.e. toward the top end of that scale. The best I've found on case consumption temperature is a figure 180 degrees C (from a US patent) = ~450 K. Hardly a requirement for hotter-burning propellant.
    And as I said, even if the temperature of the propellant gasses were higher it would indicate that the ignition temperature is likewise higher, more safe, rather than less safe.
    The Challenger incident was a case of "pure bad luck" because the wet stowage "should" have taken care of the potential problem.
    Challenger is less likely to suffer ammunition hits (cf Abrams), but if hit it's potentially more dangerous, whereas an Abrams is more likely to get ammo hits (cf Challenger), but these would be less dangerous. It's case of "you pays your money and you takes your choice"...
     

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