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New here, but I've followed this thread (and Mech Warfare) for a good while.   I attend the United States Military Academy and it is branch week here. Armor brought an M1A2 SEPv2 which, whil

Was posted on otvaga - diploma work on ramjet APFSDS design (in russian). PDF    

  • 1 month later...
On 12/21/2020 at 11:15 AM, Wiedzmin said:

115mm 3BM21M....maybe


What a strange idea to re-use the designation of an old APFSDS from the 1970s.


15 minutes ago, TWMSR said:

So Turkish bought IMI's M325 and Poongsan K277 HEAT-T ammo for their tanks. And the latter type works so-so.


Does the M325 HEAT-MP-T has pop-out fins ?


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  • 4 weeks later...
On 3/9/2020 at 7:58 AM, Militarysta said:

Posted by myself before polish made "new" 120mm Pz."xx" round:


Ca 620-640mm RHA at 2km slopped 60@ plate , but there are some news -it's two segmented as Pz.541 but this time eacht segment is made from slighty diffrent WHA alloy whit diffrent abilities to overcome diffrent type of armour:


Polish numerical simulations for the new APFSDS round against stacked RHA plates and complex targets:


1. stacked RHA

2 - 4. spaced armor arrays

5. spaced steel plates with rubber interlayers (no empty space)

6. ceramic tiles and RHA



Targets 4 and 6 cannot be penetrated, but the rest can be defeated.



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What is the purpose of the No.5 scheme (with the worst result)? When so many layers are connected with rubber, the rubber brings no benefit as the whole thing is basically one big rigid block. Isn't it so? 


Which brings a question why there is no target similar to T-72B turret inserts for example? 

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5 hours ago, Beer said:

What is the purpose of the No.5 scheme (with the worst result)? When so many layers are connected with rubber, the rubber brings no benefit as the whole thing is basically one big rigid block. Isn't it so?


This scheme is similar to BDD structure but with thicker steel plates. This type of structure greatly improves protection against kinetic rounds only when rod fractures during the penetration. It is possible when you use carbide cored ammunition instead of heavy alloy ones.





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  • 2 weeks later...

Not sure if this has been posted here before, if so, forgive me.




This is a patent by General Dynamics Ordnance and Tactical Systems Inc for a kinetic energy penetrator. 


The initial filing date is 03/08/2000 and the patent was publicized 12/16/2003, which matches up very closely with the M829A3 program. I believe this patent shows the design behind M829A3, feel free to read through and draw you own conclusions. 


Things I noted:

  • The round is shown defeating what appears to be dual-flyer plate ERA
  • It is said to have a tungsten tip and DU main rod, as opposed to the conventional idea that the tip is steel


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4 hours ago, Jackvony said:

Not sure if this has been posted here before, if so, forgive me.




This is a patent by General Dynamics Ordnance and Tactical Systems Inc for a kinetic energy penetrator. 


The initial filing date is 03/08/2000 and the patent was publicized 12/16/2003, which matches up very closely with the M829A3 program. I believe this patent shows the design behind M829A3, feel free to read through and draw you own conclusions. 


Things I noted:

  • The round is shown defeating what appears to be dual-flyer plate ERA
  • It is said to have a tungsten tip and DU main rod, as opposed to the conventional idea that the tip is steel



This is the breakaway/sacrificial tip that isolates the damage to the rod to the first third or so, right?

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7 hours ago, Collimatrix said:

This is the breakaway/sacrificial tip that isolates the damage to the rod to the first third or so, right?


Correct, according to the patent the tip segment that snaps off should make up 9-15% of the total penetrator mass. 

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  • 3 weeks later...
On 2/7/2021 at 5:36 PM, Jackvony said:

Not sure if this has been posted here before, if so, forgive me.




This is a patent by General Dynamics Ordnance and Tactical Systems Inc for a kinetic energy penetrator. 


The initial filing date is 03/08/2000 and the patent was publicized 12/16/2003, which matches up very closely with the M829A3 program. I believe this patent shows the design behind M829A3, feel free to read through and draw you own conclusions. 


Things I noted:

  • The round is shown defeating what appears to be dual-flyer plate ERA
  • It is said to have a tungsten tip and DU main rod, as opposed to the conventional idea that the tip is steel




Hmm Fig. 9 and the photo posted by Loooser of a purported M829A4.

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I don’t know where else to ask this, but how is armor “repaired” after it has been holed? Like, a vehicle was penetrated, abandoned, but successfully retrieved. Do they just plate over the hole and call it a day, or cut out a fitting that’s the shape, size, and thickness of the hole, and weld it in? Or do they just remove the whole plate and place on a new one (as with riveted armors)? 

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If you are talking about plain steel armor, the answer is the penetration area is cleaned, edges are chamfered, and a plug is inserted and welded in place. 

See page 30 here, for a quick description of steel armor repair processes. And indeed the rest of the paper for details on fused silica armor.

A note for the above: Austenitic welds are softer and more ductile than ferritic welds, but do not require the extensive and precise preheating that ferritic welds do to prevent cracking in the weld. This does however leave the weld as a somewhat weak spot in the repair.

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On Rheinmetall's 120 mm L55A1 and 130 mm smoothbore guns via EDR Magazine https://www.edrmagazine.eu/what-future-for-tank-guns-the-rheinmetall-view:



What future for tank guns? The Rheinmetall view

By Paolo Valpolini

While the appearance of the Russian T-14 Armata tank in the 2015 May Parade has definitely triggered considerations on future tank armaments requirements in the western world, penetrating the T-14 having become the benchmark, it is safe to say that the slow deployment of that weapon system makes the current threat still represented by the tanks available in numbers in Russian Army armoured formations such as the T-90M Proryv, the T-80 BVM and the T-72 B3M. This picture emerged well from the briefing provided by Rheinmetall on its developments in the tank guns field, the two speakers being Christoph Henselmann, Senior Vice-President and Head of Portfolio Tank Main Armament, and Moritz Walter, Product Manager 130 mm, both based in Unterlüss.

The western knowledge about the Armata MBT layered protection is still incomplete, while the protection level of the three in-service tanks is much better known, which is not true for that of the latest Chinese MBTs. “We consider the T-14 more an available technology rather than a real threat,” Moritz Walter says, confirming that real worries come nowadays from in-service systems. This has led Rheinmetall to a dual approach; on one hand the upgrade of the 120 mm smoothbore weapon system performances, and on the other the development of a bigger calibre gun, the 130 mm smoothbore demonstrator having been exhibited at Eurosatory 2016.



New 120 mm gun and ammunition; a 20% performance increase in the coming years

While Rheinmetall’s new 120 mm smoothbore gun, known as L55A1, is already available and is in series production for Germany, Norway and Hungary, fitted to the Leopard 2A7V MBT, the second element that will bring increased performances, the new APFSDS round, has still to come. As for the gun, Rheinmetall released the pressure differences between the L44 gun and the L55A1, which feature the same chamber volume that is of approximately 10 litres. The Extreme Service Condition Pressure (ESCP) is raised from 672 to 700 MPa, the Permissible Maximum Pressure (PMP) from 710 to 735 MPa, and the Design Pressure from 740 to 760 MPa. This pressure increase is vital to obtain the performances increases that the two rounds under development will bring with them.

The first one to enter service will be the DM73, which should reach qualification by year-end and will ensure an 8% performance increase over current DM53/DM63 rounds. However the round that will “squeeze” all the remaining growth potential from the 120 mm smoothbore weapon system will be the KE2020Neo; while the DM73 is an upgraded version of previous rounds, this one is a brand new development which qualification should start in 2024 to be completed by 2026, when it will become available on the market. The forecasted increase in performances should reach 20% compared to current armour piercing ammunition.



Why 130 mm and not a bigger calibre?

While in the interim Rheinmetall aims at improving 120 mm performances, looking further ahead in 2016 the company exhibited  in Paris its 130 mm solution, showing both the gun with a 6.6 meters long barrel, and the related APFSDS ammunition, which of course raised considerable interest. This solution does not has yet an endorsement by a potential customer; the “130” magic number is thus not the result of a requirement, but comes from a thorough analysis led the Düsseldorf-based group to orient itself towards a new calibre, and it is being proposed for the Main Ground Combat System (MGCS), or at least for its heavy armed variant, the MGCS encompassing more than one effector.

“When in 2016 we exhibited our firing demonstrator we declared that the 8% in calibre increase would have led to a 50% in performances increase,” Christoph Henselmann points out, “our aim being to bring to the target at least 50% more energy than current 120 mm rounds.” Since that date, he explains, Rheinmetall developed an expert tool that allows taking in count 50 parameters, three of them fixed, the remaining 47 variable. A tank gun is not a stand-alone system and it must cope with a series of system constraints, that in the end make the design work what Mr. Henselmann defined “an optimisation of technical compromises,” clarifying that the assumption “bigger is always better” is not in fact true.

The two key parameters for effectiveness are the aforementioned energy that reaches the target, and the accuracy at a specific combat distance, the latter requirement for future MBTs being the double compared to current tanks, so it will be necessary to hit a target with utmost accuracy at 5 km distance. A nice challenge especially on moving targets, as the flight time will be nearly the double. Among limiting factors for the gun we find i.e. weight, in the future the aim is to have systems not exceeding the MLC60 class limit, as well as turret protection, which is required against 125 mm APFSDS rounds. “Three system interface of major importance are the turret ring diameter, the recoil force and the barrel length,” Mr. Henselmann says, the diameter influencing the vehicle width and the trunnion position, the recoil forces has an impact on many aspects of the tank, not least the weight, and might bring to the use of a muzzle brake “the muzzle brake being not an advantage if you aim at optimising the accuracy of the weapon,” he underlines. As for the barrel length the most obvious impact is on the vehicle mobility, while on the gun side it influences many aspects among which the recoil force, the hit probability, the unbalance of the weapon system, the achievable muzzle energy and gas pressure. “As the result of our simulations, we carried out over 1,100 of them which considering three fixed and 47 variable data brings to over 55,000 data used for assessments, that among other showed that not all calibres fit to every barrel length.”


Christoph Henselmann states that following the R&D work done, it is quite clear that in the next 20-25 years the APFSDS round will remain the ammunition of choice for tanks against tanks firefights. “The subcalibre will stay as the best option, as it reaches the target very quickly, it is extremely accurate and the only way to defeat it is by physically destroying it.” While this is true, the APFSDS concept is far than optimal as less than 20% of the energy generated in the chamber will reach the target, he explains. Gas heat loss represents 72% of the energy loss, sabot mass 9% (for a 120 mm round) while air drag accounts for a further 3%, which means that only a mere 16% of the chemical energy generated in the chamber is brought to bear on the target. “We must therefore look at what we can optimise, and the gun calibre itself, when talking of penetrators which have a diameter of 20-30 mm has a minor importance, and by the way increasing the calibre means increasing the sabot mass, adding therefore to the loss of energy,” he explains.

He also stresses that what has to be optimised is the chamber volume, which led to the 50% increase compared to the 120 mm in the first 130 mm demonstrator. According to Rheinmetall analysis, Depleted Uranium (DU) rounds, which have an edge in current energy scenarios mostly thanks to their selfsharpening shearing capability, have reached the limit, and with the increasing energy, what Mr. Henselmann referred to as the “10 MJ scenario”, the situation should reverse with an advantage for tungsten penetrators over DU ones. It is to note that Rheinmetall aims at reaching 13-14 MJ impact energy with the 120 mm APFSDS rounds currently under development. An interesting note is that he admits that neither of the penetrators, Tungsten and DU, have been tested against the latest Russian Relikt explosive reactive armour, which apparently detonates on radar command before being hit by the incoming round.



The development work 2016-2020

Considering the development timeline of the MGCS, and knowing that developing a weapon system such as a new tank gun with its ammunition takes around 10 years, the Rheinmetall team based at Unterlüss started an intense test and development work as soon as the 130 mm demonstrator was back from Eurosatory in mid-2016. The first task was to verify the increase of performances, over 50% compared to 120 mm systems, the accuracy, and the compatibility with the weight limit considered for future MBTs. Penetration performances were assessed against NATO targets representing current threats (each costing 45,000 €), simulations being carried out shooting at 100 meters distance while reducing the charge to simulate a 1,000 meters range. As for accuracy tests, “eight rounds fall in an A3 [297 × 420 mm] sheet since the beginning of the development,” Christoph Henselmann unveils, adding that this was much better than the initial results in the 120 mm development programme. Rheinmetall engineers have a clear idea on how to proceed to further improve accuracy, “which might even bring us to downsize those solutions to further optimise existing 120 mm guns.”


From 2016 until now much effort was put in analysing data obtained with the aforementioned expert tool, in carrying out several live firing campaigns, optimising internal ballistic, the main effort being as said improving precision. Another key element was developing the autoloader, the adoption of such a system leading to a complete redesign of the breech block. This included the production of two new prototype weapons of new design, fitted with a bore evacuator, as Rheinmetall wants to have the option of a gun system apt to be used also in manned turrets. The company carried out a thorough market study on autoloaders and assessed that the most suitable existing system was produced in Southern Asia (not South Korea), Rheinmetall starting discussions with that company to find an agreement for a common development. However limits in transfer of technology from that country would not allow to meet the gun system development timeline, therefore in mid-2017 it was decided to develop the autoloader in-house, exploiting the skills of Rheinmetall Air Defence in the medium calibre field. The Swiss-based branch of the company accepted to expand its expertise into large calibre systems, and according to Mr. Walter the development went on in a very productive way bringing to the development of a functional demonstrator in the 2018-19 timeframe. “The only problem will be to convince customers that with an unmanned turret all rounds must be hosted in the turret, which means that 20-22 rounds will be available, as a bigger ammunition magazine for the autoloader would not be system compatible in terms of turret dimensions and hence added armour weight,” Christoph Henselmann explains, and this means less than half the available rounds on current four-man crew tanks. “Since early 2020 the autoloader has been transferred to Unterlüss and has been connected to the gun for testing, and in fall 2020 it was used on the firing rig for live firing. “We still see some challenges in its development, but we are not facing major hurdles,” Mr. Henselmann says, explaining that problems should be overcome to cope with the MGCS development timeframe.

Comparing pressure levels in the L55A1 gun and in the 130 mm L52 prototype, Extreme Service Condition Pressure climbs from 700 to 800 MPa, Permissible Maximum Pressure from 735 to 850 MPa, Design Pressure reaching 880 MPa compared to the 760 MPa of the 120 mm system, an average increase of 15%, with a chamber volume of “15+X” litres compared to the 10.2 litres of the 120 mm solution, the “X” leaving the door open to further refinements. The higher pressure of course requires the use of different material as all components, including ammunition elements such as primers, have to be pressure-hardened to withstand new operating pressures.



The way ahead

Shifting from technology to market requirements, Moritz Walter points out that Rheinmetall’s analysis shows that for newly built MBTs the unmanned turret solution should be the preferred option, while for current MBTs upgrade the manned one is definitely the most probable. That said, the upgrade option would definitely require a wholly new turret, as the 130 mm gun fitted with its autoloader that would not fit in existing turrets.

Christoph Henselmann also clarifies the appearance of the 130 mm on a video showing a Challenger 2 fitted with the new gun. “In April 2020 we had a window of opportunity when the Challenger 2 was in Unterlüss and no further tests were planned, to install the 130 mm on it, following the clearance from the UK customer. The British tank is a little wider than the Leopard 2, making things easier,” he says. Within the limited three weeks time the work concentrated on verifying how the 130 mm gun is well balanced inside a current 120 mm turret, checking stabilisation.

The main objective for Rheinmetall is the MGCS programme, in which the 130 mm competes against Nexter’s 140 mm proposal. “We consider that currently the overall 130 mm system has a TRL 2-3, the weapon more towards 3 while the autoloader being closer to 2,” Christoph Henselmann says, explaining that in February 2021 Rheinmetall started for the first time direct negotiation between the industries of both France and Germany. “In two years time, in late 2022, we expect the bi-national customer to decide which will be the main armament calibre, but simultaneously we are working on an upgrade solution for in-service 120 mm platforms,” he adds, stressing that the weapon system for manned turrets will not be completely identical to the one being proposed for the MGCS, the fitting of the 130 mm gun in a manned turret being less optimised that in an unmanned one, thus requiring some adaptations.

Rheinmetall also maintains a close eye on developments ongoing over the pound, and has already presented its solution to the US Army, as a potential candidate for what is currently referred to as Optionally Manned Tank.

“Both 130 mm systems will reach TRL 6 in the mid of the current decade, allowing for qualification of the gun system inside the weapon system,” he announces. “At this stage, although the development is not completed, we can safely say that the 130 mm allows a considerable increase in performances even at longer combat ranges, and we are more than confident that we are able to fulfil the requirements to double that range,” Christoph Henselmann concludes.


I guess the old DM63 Plus APFSDS was turned into the DM73 (8% improvement, using old penetrator + more powerful propellant charge) and the old DM73 was turned into the KE2020Neo aka DM73Neo (20% improvement in penetration thanks to a new penetrator and more powerful propellant charge).

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Very interesting article, also has good info for MGCS:


- Weight within limits of MLC 60

- The turret will have protection vs 125mm APFSDS (even if it is unmanned as the rheinmetall concept envisions)

- 99 percent implied that the autoloader is based/inspired on the Japanese Type 10´s but still is an original design (that´s what i call a discreet F-U to the French and their experience with the Leclerc).

- Ready to fire ammo not exceeding 22 rounds.

- Development of the tank is expected to continue at least until 2026.

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    • By SH_MM
      [title image]
      Hollow charges and armor protection - their alternating progression
      The term "hollow charges", which is commonly used in German, is not very accurate for the explosives so called. The somewhat more general American term "shaped charge" is a better description of the measures necessary to achieve the desired effects with these charges. Apart from the explosives used by glider pilots at Fort Emeal, it is of great importance for the vast majority of the extensive and versatile range of applications of shaped charges developed since the Second World War that their suitably shaped surface is covered with a layer of inert materials, preferably metals.  The individual elements of the liner are accelerated to velocities of several km/sec and, through special selection of the initial shape and dimensions, it is possible to transform these liner bodies into projectile-like structures which are best suited to combat the respective target.
      This possibility of adapting the effector to the structure of the target to be engaged is very important for the use of hollow charges, but the application potential of these charges, given their early and impulsive nature, is far from exhausted by what has been developed in this field so far. This is particularly true when it comes to combating targets whose design is already tailored to protect against the known hollow charges.
      This will be explained in more detail below; in addition, examples will be used to illustrate the many different ways in which explosives can be used to obtain targeted effects and counteractions.
      The effect of explosive devices attached to armour panels - the "spalling effect"
      In most cases of using detonating explosives, the energy released by the detonation is transferred to inert materials. In the case of armour plates on which explosives are detonated, the direct effect is relatively small. Although the detonation pressure exceeds the strength of the armour material many times over, the material goes into a state of fluidity and is slightly pressed in at the surface - something similar happens when damp clay is pressed. The depressions that occur are small because the time during which the detonation pressure is sustained and the material is in a flowing state is very short. This only lasts until the relaxation of the highly compressed explosive decomposition products towards the free surface of the detonator has taken place. If, for example, an explosive layer of 2 cm thickness is placed on an armour plate, the impact time on a surface element of the plate during detonation is about 2/800000 sec, i.e. 2.5 µsec. During this time only a slight displacement of the plate material can occur. The example of an explosive layer applied to the surface of an armour plate and detonated there is also suitable for explaining a phenomenon that is very important and is referred to several times in the context of the present comments:
      [Figure 1]
      Under certain conditions, material parts detach from the rear side of the armour plate and are propelled at quite high speed into the space behind the plate. This so-called " spalling effect " occurs whenever a limited area in a body, where the material is under very high pressure, reaches a free surface of the body (see figure 1). There, the material parts compressed under high pressure relax and advance perpendicular to the surface. The relaxation is thus associated with acceleration. While the relaxation spreads into the interior of the pressure area, all material parts that have been compressed by it are accelerated. If the relaxation wave reaches the rear end of the pressure area, i.e. the zone in which the material particles are not compressed and therefore remain at rest, the parts that have been set in motion by the relaxation break off at this point and continue their motion only outside, provided that the tensile stress that occurs exceeds the tensile strength of the material.
      In the case of the spalling effect, one observes a separation of disc-shaped plate parts on the back of an armour plate exactly opposite the surface covered by the explosive on the upper side (see also Figure 15). This surface must not be less than a certain size, because the accelerated, spalling parts must not only overcome the tensile strength of the detachment from the inner plate parts, which remain at rest, but also the shear stresses at the edge of the spalling plate. In general, this is only then the case when the diameter of the overlying explosive layer exceeds the thickness of the armour plate, otherwise a " bulge" appears on the underside of the plate.
      The effect of the " squash head " projectiles is based on this spalling effect. The explosive in the bullet cap is released when the projectiles impact on of the armour plate is spread and then detonated. 1)
      The effect of unshaped, uncontained explosive charges in the free atmosphere

      If an uninsulated explosive device is detonated in the open atmosphere without any special design or arrangement, its effect is relatively small at a distance from the source of detonation. Although the pressure behind the detonation front, which in modern explosives can reach speeds of is advancing at about 8 km/sec, is quite high. It is in the order of several hundred thousand atmospheres, but it rapidly decays as it spreads in all directions, distributing energy and momentum over areas that grow quadratically with distance.
      By contrast, special arrangements, which should be mentioned here because they are to a certain extent related to hollow charges, can be used to achieve a sufficient pressure effect even with unshaped, unchecked explosive charges at greater distances, for example against flying targets.  If, for example explosive charges are arranged at the corners of a regular polygon and detonated simultaneously, a very effective superimposition of the pressure occurs on the axis of symmetry of the arrangement at distances of up to several diameters of the polygon - in the so-called Mach area. Towards the end of the Second World War, the possibility of using such charge arrangements from the ground against enemy aircraft flying in pulks had been considered. In model tests with 6 charges of 50 kg trinitrotoluene (TNT) each, regularly distributed on a circle of 100 m diameter, a pressure of about ~15 bar was measured 350 m above the ground in the vicinity of the axis of symmetry.
      Protective effect of multilayer armour

      In order to be protected against the spalling effect of squashing head projectiles and similarly acting warheads, it is advisable to provide armour which consists of at least two layers with a gap between them. For this reason alone, the development of anti-tank ammunition was therefore based on paying special attention to multilayered armour. The requirement for penetration of structured armour with air gaps is also indispensable in other respects. The same conditions apply, for example, when an armour is hit by a plate covering the running gear or by a "skirt" attached to the running gear. In the case of more or less abrupt impact, the point at which the ignition of a shaped charge warhead takes place can then be up to several metres away from the point at which its main effect should begin. In addition to standard single-layer targets, the testing of hollow-charge ammunition therefore includes targets consisting of several plates spaced at certain distances from each other (see Figure 2).
      [Figure 2]
      In principle, the mode of action of hollow charges meets the above-mentioned requirements very well, much better than is the case with conventional impact projectiles. When a kinetic projectile hits a armour surface, a high pressure is created in both the armour material and the projectile. Starting at the tip, a pressure condition is built up in the bullet, which leads to the phenomenon described earlier in the treatment of the spalling effect on the free surface of the bullet. Tensile stresses occur which begin to tear the bullet body before it has penetrated the target surface. They can cause the bullet to disintegrate into individual parts after penetrating the first plate, which are then stopped by a second plate of a multilayer target (see Figure 3 a and b).
      [Figure 3]
      If, on the other hand, hollow charges with a lined cavity are detonated on the target surface, the so-called hollow charge jet is generated, which is sometimes called a "spike" because it is initially coherent and usually occurs in a solid state. With the hollow charges commonly used today, the jet disintegrates as it advances into a series of small - often spindle-shaped - very fast projectiles, whose frontal velocities can reach about 10 km/sec; the last ones still achieve about 2 km/sec. When the first particle hits the surface of the shell, a pressure in the order of 1 million atmospheres is created there; the shell material begins to flow and an approximately tulip-shaped crater is formed, similar to the penetration of a body of high velocity into water. The volume occupied by the crater is released by displacing the armour material towards the free surface. When the second jet particle hits the bottom of the crater, repeat the process, as well as the impact of the following particles. Each particle continues the displacement of the target material where the previous one stopped until schliefilich creates a channel of penetration through the whole plate.
      The flow of the material particles associated with the displacement of the target material ends at the free surface. Partly at the upper side, partly at the lower side of the armour plate and partly also at the already created penetration channel, which is subsequently narrowed again slightly.
      The following jet particles not consumed during penetration continue their path after passing through the penetration channel and act on obstacles that are on their path. If they hit another armoured plate, they can continue the penetration process there undisturbed.
      In contrast to the behaviour of the compact kinetic projectile, the individual elements act on the armour one after the other, independently of each other, and it does not seem so important at first whether the armour is massive or in separate parts, because a disturbance at the tip of the projectile does not affect the following parts.
      Nevertheless, the so-called "bulkhead armour", in which a number of thinner armour plates are arranged with air gaps between them, also provides increased protection against hollow charges: The penetration channel created by the impact of the particles of the hollow-charge projectile is relatively narrow and is of the same order of magnitude as the plate thickness when using thinner plates of the bulkhead armour. When the hollow-charge particles strike these thin plates, the hole in the plate is created essentially by the fact that the material elements of the plate which are caught by the high dynamic pressure are forced away from the plate under the influence of the tensile stress acting perpendicularly to the free surface, both on the upper and the lower side of the plate. The penetration channel therefore runs almost perpendicular to the plate surface, regardless of whether the hollow charge particles generating the pressure impact obliquely or vertically. The tensile stresses induced at the plate surface as a result of the dynamic pressure are in any case perpendicular to the plate and also have an effect in this direction (see Figure 4).
      [Figure 4]
      If now diagonally incident subsequent particles reach the previously created penetration channel running approximately perpendicular to the surface, they find a much reduced cross-section for their passage compared to the vertical incidence (see Figure 5). There is thus an increased probability that they will come into contact with the wall as a result of path variations, as a result of which their contribution to the penetration performance is lost. The affected particle disintegrates explosively, since - as described above - the high pressure occurring during wall contact induces tensile stresses on the free surface of the particle, causing it to burst. In Figure 6, a TRW image converter camera is used to illustrate how a steel ball of 2 mm diameter is sprayed after it has penetrated a very thin plastic film at very high speed. Figure 7 shows the piece of a hollow charge jet in which a similar burst was triggered on a particle by touching the wall. As can be seen from the figure, the small debris of the disintegrated particle spreads sideways to the direction of the beam, apparently away from the wall that was touched. It is important that the propagation of these fragments into the free space behind the plate is possible. At massive targets this free space is not available, the particle splinters would be held together and their impulse could contribute to the penetration even if the particle had touched the wall before. That's why it's important, armoured plates and air gaps of certain thickness should follow each other.
      [Figure 5, figure 6 and figure 7]

      This leads to bulkhead arrangements which, when hitting the wall at an angle, cancel out the effects of a high portion of the hollow charge jet due to the increased probability of the jet particles touching the wall and their subsequent disintegration into the gap. The weight of the armour required for this, in relation to the unit area, is considerably less than in the case of solid armour. It is essential that this provides increased base protection against both balancing projectiles and shaped-charge ammunition, and it is noteworthy that this effect occurs in both cases by inducing the decay phenomenon on impact at high velocity. However, in the case of a balancing projectile, the entire mass of the energy carrier is captured by the destructive tension waves on first impact, whereas in the case of a hollow-charge jet only the mass portion corresponding to the respective impacting jet particles is captured.
      Measures to avoid disturbance of the shaped charge jet

      However, it is not clear why rear particles of the hollow charge jet must necessarily come into contact with wall elements of the penetration channel created by the previous ones. Should it not be much more possible to ensure that the particles
      aligned very cleanly and without "staggering" movement exactly on the cavity axis? However, this means that the slightest deviations from central symmetry must be avoided in the structure of the hollow charge. The whole rigor of this requirement is that it relates not only to the dimensions of the charge, but also includes the homogeneity of the materials used and that - as has already been shown - even differences in the size and orientation of the crystals in the explosive and in the copper of the liner have an influence. This requirement is even more stringent if one takes into account that the properties of the crystals mentioned above change over time, i.e. as they age, and that changes are also triggered during processing. A very sensitive influence can also be expected from the way the detonation is initiated.
      With the aforementioned and similar requirements with regard to precision, the production of hollow charges has set goals whose pursuit in the past has already brought about significant progress with regard to the generation of an undisturbed hollow charge jet during detonation, and in the future, through the tireless efforts of research and technology, even further perfection can be expected. In addition to this somewhat utopian-looking reference, however, it must be emphasized that the hollow charge principle is very flexible and includes a wealth of other possibilities for counteracting disturbances which oppose the effective targeted use of the explosive energy released during detonation. For example, it is not necessary for the hollow charge jet to dissolve into a number of particles as it progresses. Some of the irregularities in the behaviour of the particles will only develop during the tear-off process and can be avoided if the hollow charge jet is constructed in such a way that it does not tear.
      The reason for the dissolution of the hollow charge jet into a number of particles of different velocities is that the individual jet elements already have a different velocity when they are formed. In the case of the hollow charges currently in use, there is a velocity gradient in the beam from about 8-10 km at the tip to about 2 km at the end.The consequence is that the jet is constantly stretched as it progresses and eventually dissolves into more or less parts according to the strength properties of the material .2)
      The programmed shaped charge jet

      By special selection of the parameters of a hollow charge (type and density of the explosive, dimensions and shape of the cavity, wall thickness and material of the cavity lining, shape as well as wall thickness and material of the casing, position and extension of the ignition elements) it can be achieved that differences in the velocity of the individual elements of the jet are prevented at all.
      The relationship between the distribution of mass and velocity in the jet and the charge parameters was already known shortly after the discovery of the
      the lining of the cavity achievable effect by Thomanek quite detailed results. 3)
      This connection is achieved by following each individual sub-process during the detonation of the charge and the deformation of the liner by calculation. When the detonation front reaches the individual zones of the liner body, the material there enters a state of flow under the influence of the detonation pressure and is accelerated inwards. The speed at which the lining elements are accelerated depends on how long the pressure remains at the zone under consideration or, which comes to the same effect as how far the outer surface of the detonator is from this point. Thus, the influence of the width of the explosive coating on the velocity of a panel is obtained.
      For example, consider a cylindrical charge with a cone as a cavity and a diameter of 8 cm. The time required for the dilution wave to reach the top of the cone from the outer surface is then 4 cm/approx. 800000 cm/sec, i.e. approx. 5 microseconds; in the central zones of the cone with an explosive coating of 2 cm, this time is only half as long and the impulse transmitted to the lining elements by the detonation pressure in this time is therefore half as large.
      Of course, the speed also depends on the wall thickness of the lining body at this point and the density of the lining material.  The initial velocity of the lining elements can be specifically influenced by a suitable choice of the wall thickness and it can change at will between the tip and base of the lining cone. One speaks of "progressive" or "degressive" liners, depending on whether the wall thickness increases or decreases towards the base. The influence of the liner's wall thickness/explosive coverage ratio then has a further effect on the jet elements that are emitted when the liner zone converges on the cavity axis. In addition, the mass and velocity of the jet elements formed depend on the angle at which the convergence takes place, i.e. the opening angle of the cavity. Peak angles result in high velocities for small masses, and the opposite is true for obtuse angles.
      The previous remarks should serve to explain, at least by way of indication, how it is possible to determine the dependence of the distribution of mass and velocity in the jet on the charge parameters. With the knowledge of these interrelationships, it now seems possible to create projectile-like structures from the cladding bodies, in which the initial length and the distribution of mass and velocity over this length are predetermined, i.e. the hollow charge jet can be programmed.
      Up to now, almost all attempts have been made to obtain a jet with the greatest possible penetration capacity. This led to the familiar design forms: cylindrical on the outside, cavity for example 60° cone with copper liner, initiation of the detonation now often by detonation wave deflection at the rear edge of the detonator, whereby better use of the explosive volume and higher beam tip velocities are achieved (compare also Figure 16). The resulting beam is then a constantly stretched structure with a velocity of up to 10 km/sec at the tip and about 2 km/sec at the end, which is followed more slowly by the rest of the cladding mass, the so-called "slug". 4)
      As already mentioned several times, the differences in the velocity of the individual beam elements cause the initially coherent structure to be broken up into a sequence of particles. Nevertheless, very good results have been achieved with the described type of charges, especially against massive targets.
      Penetration depths of up to 6 charge diameters have been achieved. In contrast, when using targets with air gaps, the distance travelled in the massive parts of the target is greatly reduced. In the future, requirements for the performance of hollow-charge ammunition should be geared to these reduced amounts; this would mean that modern hollow charges should be developed to penetrate structured targets rather than exaggerated penetration performance in massive targets. An attempt should be made to program the hollow-charge jet, i.e. to adapt it to the structure of the target.
      In the following we will try to explain by means of examples that there are many possibilities to modify the beam of the currently used hollow charge.

      A completely different motion sequence of the particles of the beam from this type of charge can be obtained by replacing the centrally symmetrical ignition by a (one-sided) eccentric one.The individual beam particles then no longer move one behind the other on the cavity axis, their paths point in a fan-like manner in different directions (compare Figures 8a and b) 5) The following example is intended to show how even a slight change in the cavity shape can noticeably influence the beam and its effect.  Figure 9a shows a cladding body whose shape can be roughly described as a cone which ends at the base in a spherical zone. Figure 9b shows the penetration channel of an externally cylindrical charge produced using this liner.
      [Figure 8 and figure 9]
      The explanation for the peculiar shape results from the velocity distribution in the hollow jet. The front part of the jet comes from the cone-shaped part of the cavity and corresponds to the jet from a cone, which stretches as it advances. For the subsequent jet elements, which originate from the spherical zones at the base, it is decisive that the tangent at the cavity becomes steeper and steeper towards the base. The consequence is that the successive jet elements become faster and faster towards the rear, thus approaching each other and leading to a thickening of the jet in this rear area. On impact, the effect is increased in the form of a widening of the penetration channel.
      While with the hollow charge described above, a concentration of energy occurs in the rear jet section, it is also possible to achieve this in the front jet section. For this purpose, the cavity must be spherical at the apex and end in a cone at the base (see Figures 10a and b). The penetration channel is wide at the top and has the shape of a hemisphere followed by a narrow conical part. 6)
      If the cavity, which is essentially delimited by a cone, is spherical at both the apex and the base, the penetration channel will consist of a wide part at the armour surface, followed by a narrow conical part and a further widening at the end. Following these examples, it should be considered possible that the effectiveness of the individual sections of the hollow charge jet can be determined in quite a different way, especially if it is taken into account that other parameters of the hollow charges can also contribute to this by their specific choice.
      [Figure 10]
      As explained in the previous section, other velocity distributions are possible in addition to the velocity gradient in the jet of the commonly used hollow charges that leads to rupture. It is also possible to achieve that all beam elements have the same velocity, provided that the relevant charge parameters are adjusted to it in each zone of the cavity. If, for example, the wall thickness of the cladding is selected in such a way that it is in the same ratio to the corresponding width of the explosive coating for all zones, the cladding elements of all zones receive the same initial velocity on detonation and thus also all the beam elements that are separated from them when flowing together on the cavity axis.
      As a result, the jet is represented here by an "overlong projectile" with a rather high velocity. A sketch of the principle of such a charge is shown in Figure 11. The nozzle-shaped body attached to the base has the purpose of preventing the decomposition by-products from coming into direct contact with the free atmosphere when the base zone is accelerated, thus avoiding a premature drop in pressure. In a similar way, other causes of disturbance are to be avoided, whereby a number of experiments are always necessary before a principle path can be realized.
      [Figure 11]

      Instead of a single rod-like projectile, a sequence of several such rods can be obtained in which the individual elements have the same velocity, with the velocity of the rods differing from each other.
      In addition, from the special solution of the identical velocity of all beam elements, transitions to the common hollow charge with the large velocity gradient in the beam can also be developed. In particular, the case can also be realized in which the difference in the velocity of the following beam elements is so small that the beam is only broken when all obstacles of the target have been overcome. How such a continuous beam reacts to protective measures that disturb a particle-dissolved jet is still to be investigated. In any case, the disturbances caused by the rupture process are avoided here (compare Figure 12).
      [Figure 12]

      Also, the range of possible variations in the structure of the shaped charge jet is so wide that an adaptation to very different target compositions seems possible. Not insignificant is the fact that the energy of the effect carriers from a hollow charge can be distributed in a targeted manner to mass and velocity, i.e. the jet can obtain a greater mass at the expense of the velocity of its elements and vice versa.
      As investigations have shown, the protective effect of certain materials depends on the speed of the projectiles. 7) However, such measures need not refer to the entire jet, but can be limited to parts of it, for example to the front or rear parts of the target.
      A special group of shaped charges has not been mentioned so far, namely those with a flat, especially blunt conical cavity. ln contrast to the pointed conical cavity, the attainable velocities are lower here. The speed of the structure previously referred to as the jet is no longer very different from that of the so-called following slug. It can be achieved by methods which will not be discussed in detail here, that the jet and slug components - i.e. the entire mass of the liner - merge into an at least temporarily coherent structure. lf the difference in the speeds of the front and rear parts is sufficiently small, it is absorbed by internal expansion work, and a projectile with a uniform speed of about 2000 m/sec is created. Figure 13 shows a series of such projectiles from charges with a flat cavity, using X-ray flash images.
      Figure 14 shows a section through a captured specimen of cohesive projectiles. Such projectiles are particularly characterized by stable flight at long distances and have already found 'a versatile application today, especially as a replacement for natural fragments (see also cover picture and Figure 15).
      [Figure 13, figure 14 and figure15]
      In connection with the efforts to combat future targets, which may be unknown at present, it should be mentioned that it is possible and possibly very useful to arrange projectile-forming hollow charges in a special way one behind the other. If this is done taking into account all the side effects of the detonation, and if such an arrangement is ignited appropriately, one obtains a sequence of projectiles flying one behind the other at fairly high speed, the mass of which is considerably greater than that of particles of the hollow charge jet.
      It is also possible to combine a projectile-forming charge with a jet-forming charge with an acute-angled cavity. Figure 16 shows such a charge, also known as "tandem charge".
      It was designed to create a strong follow-on effect inside the tank. On detonation, the jet from the rear charge penetrates through an opening in the apex of the front flat-cone charge. Only after this has been done is this charge also detonated; the flat liner body is formed into a projectile which follows the jet from the rear charge through the channel created by it and comes into effect there depending on the intended purpose.
      [Figure 16]
      These examples are intended to show that there are almost no limits to the imagination when it comes to exploiting the potential inherent in the principle of forming effective projectiles by transferring explosive energy to inert materials. There are many ways to develop explosive charges that can be effective against complex targets and do not necessarily require a gun to reach the target, but can be used in warheads of missiles. Of course, there will always be possibilities to achieve sufficient protection by suitably constructed armour. What should be particularly emphasized here, however, is the view that there is hardly likely to be a miracle cure for all types of shaped charges and that, apart from a temporary predominance on one side or the other, there will probably continue to be mutual efforts to perfect shaped charges on the one hand and protective armour on the other.
    • By Ronny
      I see many knowledgeable members here so i decided to make an account to ask some question
      According to many historical accounts, the armor of WW II battleship is very thick: can be between 410-650 mm of steel
      Thick enough that they can even resist penetration  from 12-16 inch canon 

      Compared to these massive round, it is probably obvious that missiles such as Harpoon, Exocet will do little or nothing against the armor belt: No penetration and probably nothing more than a small dent.
      Anti tank missiles such as AGM-65, AGM-114 or Brimstone can penetrate the armor but all their warhead will do is penetrating a tiny hole into the massive battleship, it likely will hit nothing significant given that a battleship have massive volume of space). Furthermore, i heard space armor is extremely effective against HEAT warhead as well).
      But what if the two are combined? HEAT + explosive warhead: aka BROACH.
      With a frontal shape charged and secondary follow through bomb
      This is the working principles of the system:

      BROACH was designed to help small cruise missile penetrate bunkers. So i have some question:
      1- Because concrete and soil are very brittle, unlike steel, I think the precursor charge likely much drill bigger hole in them than it can drill on steel armor belt of a battleship, so even if we use missile with BROACH warhead to hit a battleship, it won't drill a hole big enough to allow the secondary warhead to pass through. Is that a correct assessment?
      2-  Looking at the cutaway of the missiles. How come the detonation of the frontal shaped charge doesn't damage/destroy the secondary warhead or at very least propel it to the opposite direction? 
      3-  Can supersonic missiles such as Agm-88 (Mach2) , Asmp-A (Mach3) , Rampage , Asm-3 (Mach 3) , Hawc (Mach 5) penetrate the armor belt of a battleship? or they simply don't have enough velocity and density?
    • By Molota_477
      M1 CATTB
      pic from TankNet.
      I feel uncertain whether its cannon's caliber was 140mm or not, I found a figure at the document AD-A228 389 showed behind, which label the gun as LW 120.But in many ways I've found its data in websites all considered to be 140mm.

      AFAIK,the first xm291(140)demonstrator was based on xm1 tank, and the successor was the''Thumper'' which was fitted with a new turret look like the CATTB but still m1a1 hull(Maybe it was CATTB's predecessor? )

      I will really appreciate if anyone have valuable information to share
    • By Domichan
      Hello all,
      I apologize for the fact that my first post is a question. I am a Dutch collector of medium and large calibre AP ammunition and I recently bought an 105mm APFSDS-T projectile, that is marked with the designation DM53. The 120mm DM53 is well known, but I cannot find any information on the 105mm DM53. I do know the IMI M426/DM63 round exists, for I have seen pictures of that, which would indicate that a DM53 would exist as well, in accordance with the way German ammo designations go. Questions to Rheinmetall, the Bundeswehr and various collector groups have remained unanswered. 
      Among the experts here, is there anyone who has information on this type of APFSDS-T Round?
      Thank you in advance,

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