SH_MM

Yes, I was talking about that. The picture is showing a snipplet from a research paper that involves both Deisenroth and Condat Scheyern, two companies involved with the Leopard 2A5's survivability upgrade. The array consists of two sandwich plates, each formed by two steel plates with 10.5 mm steel with yield strength of 1,200 MPa and either seven or eight milimetres thick layer of elastic material (five different materials were tested). Both sandwich plates are spaced 30 mm apart, the whole array is sloped att 65°. The overall thickness of this array seems to be identical to the thickness of the two frontal NERA plates (and empty space) at the front of the Leopard 2A5's wedge-shaped add-on armor modules. Not regarding the armor of the Leopard 2/Stridsvagn aside of (incorrect) internet estimates for the Leopard 2A0 armor protection. That is probably a mistake caused by the hatch sliding mechanism sitting in front of the hatch. On the Leopard 2 up to (and including) the 2A4 variant, the hatch swivels. The new sliding hatch adopted with the Leopard 2A5 requires a different mechanism, which is mounted in front of the driver's hatch (and also the hatch itself seems to have become a bit thicker). So measuring what is in front of the hatch doesn't equal the thickness of the hull armor. On the Dutch and German Leopard 2A5, the hull armor wasn't changed compared to the "C" and/or "D-1" generation original layouts. The Leopard 2A6NL is - like the Germany Leopard 2A5 and Leopard 2A6 - built to the Mannheimer configuration, hence the hull did not receive an add-on armor module and is largely unchanged (aside of the new hatch and rear drive camera) compared to the later batches of the Leopard 2A4. The Dutch tanks originally had "B" generation main armor, but apparently this was changed (the heavy skirts of the "C" generation were adopted, so base armor might also have been altered). The turrets likely have "D" generation main armor like the German model. I don't think they offered all combinations of armor, that clearly wouldn't make sense. The LOS thickness of the base armor on the right thickness is higher, once an armor block was added in front of the optic. According to the analysis from Laviduce, the right turret cheek of the Leopard 2 with "B" generation armor already offers a higher level of protection than the left cheek, which makes sense (below the optic, the LOS is 1,100-1,200 mm - including an empty space, but that would also improve protection a bit). Edit: Seeing you have posted a measurement of the M1A2's hull armor on another forum, it seems confirmed that the LOS thickness of the M1IP/M1A1's hull was increased compared to the M1 Abrams measured by the War Thunder developers.

Unless you have seen different documents than me, the statement comes from a document written in 1970, when the Keiler/Leopard 2 was expected to enter service before 1975 (and as a matter of fact was still using simple space armor, using MLC50 as upper weight limit). They stated that it would be possible to modify the design (to include Burlington armor) and put it into production by 1975. No, the seat is located in the same space. The additional volume above it is completely occupied by the armored hatch I believe it is impossible to achieve the protection level of the Swedish tank just by adding the Leopard 2A5 wedge armor to a Leopard 2A4 with "B" generation armor. It just isn't very thick, IBD Deisenroth tested a double-layered NERA array in the 1990s, which consisted of two sandwich plates (10.5 mm semi-hardened steel + 7-8 mm special material + 10.5 mm semi-hardened) - this might be related to the wedges, the overall thickness considering the slope (65°) seems to match the Leopard 2A5's wedge armor. Such an armor array would not be suitable for providing 400-500 mm steel equivalent protection (given that the Swedish MBT reaches 800-900 mm vs KE from the front). The third NERA layer doesn't actually cover a lot of frontal surface and might be adopted to improve the protection of the mantlet along the frontal arc. Still the slides say that the Leopard 2 "Swedish model" has at least 700 mm protection along the frontal 30° at the left cheek compared to 0° for 700 mm protection for the left cheek of the "German model". He also mentions that according to his understanding the Stridsvagn 122 uses titanium armor (Ti-6Al-4V) and that the high protection requirements meant that turret and hull had to be newly built, because it wasn't possible/practical to convert existing Leopard 2s to this configuration. I don't know what you mean with "front hull roof was increased". The driver's hatch was altered, the side skirts aren't actually heavier given that the frontal elements are fitted to the Leopard 2A4 with "C" generation armor (and armor changes to this variant supposedly was weight neutral compared to the earlier model) and the rear section of the new skirts adopted on the 1991 model of the Leopard 2A4 has been described as "lighter" [compared to earlier variants]. The weight of a Dutch Leopard 2A6 turret is something like 19.75 tonnes compared to 15.5 tonnes for the original 2A4 (B) version. The Stridsvagn 122 doesn't feature a mine protection. The Strv 122B (4 Strv 122 tanks converted) features the same mine protection kit as the Leopard 2A6M, the combat weight is above 64 tonnes. If they decided to use a German army version, yes. But the KVT/IVT and TVM Max. were all available with IFIS (C4I) and armor modules covering the roof and hull aswell. For the Leopard 2 with "B" generation armor, there wasn't a combination, because the base armor wasn't combined with anything. The Leopard 2 "German model" with "B" base armor (located in column 1) and "D-2" add-on modules (located in column 4) has the technology combination 5, which is why I think that it is the sum of the columns numbers (1+4).

West-Germany got access to Burlington armor beginning in 1970 (selected scientists) and started developing a common MBT with the UK between 1972 and 1977. When the West-Germany first announced that they had developed a composite armor package for the Leopard 2, the UK assumed that it was heavily based on the knowledge and technology used for Burlington, acquired during the early 1970s. However West-Germany claimed that this armor was a local development, probably based on the fact that Dr. Manfred Held (the inventor of modern ERA, as the Soviets ceased ERA research at the end of the 1950s) patented NERA in 1973. The Leopard 2 TVM Max. was tested in Sweden, which was based on the chassis number 11156 and therefore belonged to the last production batch (with what I believe to be "D-1" type armor). As the TVM Max. returned to Germany after the Swedish trials, it seems that Sweden only tested armor arrays representing the corresponding Leopard 2 tanks rather than firing at real tanks - the same happened with the M1A2 Abrams. Reading through Richard Lindström's article and a few German sources, it seems that only a single Leopard 2 was send to Sweden. Therefore the tested armor arrays and thte actual tank tested by Sweden might be independent from each other. I don't think that "German model" and "Swedish model" actually refers to "tank that Germany wants to sell to Sweden" and "tank that Sweden wants to buy", but rather to "Leopard 2 version currently considered for adoption by Germany" and "Leopard 2 version suggested by Krauss-Maffei for Sweden". This seems to be a case of common excuses from people pretending that their own military always makes the right decisions and has infinite budget, while all others are wrong. The increase in profile is irrelevant, given that there is no protected volume behind the roof modules in the horizontal plane. Given that the PERI was raised on the Strv 122 + TVMs with roof armor, there also wouldn't be a negative difference in terrms of situational awareness. The Panzerhaubitze 2000 has received similar thick roof armor without issues, the Puma also features some (albeit thinner). The roof armor would likely be included in a 140 mm variant projected during the 1990s to arrive in active troop service by 2008, but canceled when the NGP project was started. I don't think it is reasonable to argue with LOS efficiency in case of the wedge-shaped add-on armor. Unlike the base armor, the majority of its volume is hollow, the actual LOS thickness is variable depending on impact location (the maximum LOS is only reached at the center; hitting above or below it, the overall LOS will decrease massively). In terms of function, the armor is ought to be much more comparable to heavy ERA, i.e. weakening the incoming projectile in such a way that the base armor can defeat it. There are several reasons why I don't agree with your theory. I don't think there is actually any actual proof that there were different add-on modules being tested on the Leopard 2 Improved protoypes. While the table format chosen by KMW suggests there might have been more than just one type of add-on armor, it also includes slots/positions for "B" and "C" technology Vorsatzmodule. External the only differences between the Leopard 2 Improved prototypes and the series production models is the shape of the side add-on armor modules. which have become thinner (!) on the series production version. I'd argue that these changes could have been made to reduce weight and do not indicate any change in the composition or effectiveness of the frontal add-on armor modules. For the "German model"/KVT, the "B" armor package improves protection from ~450 mm vs KE at the left turret front to 862 mm vs KE. If we assume the same relative increase at 30°, the protection level is only at best 668 mm vs KE (the Swedish documents noted that the left turret cheeck of the "German model" of the Leopard 2 Improved is only capable of stopping an APFSDS with 700 mm penetration into steel at direct impact from the front) - please note that the efficiency of the add-on NERA probably decreases when hit from an angle, because the LOS thickness of the NERA plates is reduced, the thickness of the empty space is reduced and (most importantly) the lower angle means less material is forced into the path of the penetrator. That's why 862 mm vs KE from the front could be as low as 600 mm vs KE at 30°. The "Swedish model" is capable of providing 720 mm vs KE at 30° impact angle. Comparing the right turret cheek armor at 0° might be misleading, because their was a new armor block added when the EMES-15 sight was raised. But again the "Swedish model" is a lot better protected against attacks from an angle (810 mm vs KE at 30° compared to 758 mm vs KE at 20°). According to Rolf Hilmes' 2007 book "Kampfpanzer heute und morgen: Konzepte - Systeme - Technologien", the Stridsvagn 122 has a higher level of ballistic protection than the German Leopard 2A5 while mentioning the increased roof and hull armor as separate points. Weight. The Leopard 2A4 with "B" generation armor weighs just 55.15 tonnes. The weight of each frontal add-on armor module for the turret is about 500 kg as revealed by the Dutch army. Estimated weight of boith turret side add-on armor modules is less than 500 kg combined (they cover a similar area as the frontal modules, but are made of a single NERA layer instead of 2-3 and are less sloped). Given a combat weight of 62.500 kg, the weight of the hull add-on armor and roof armor would be about 5.85 tonnes. Comparing the weight differences of several other versions suggest that is incorrect (for example the Leopard 2A5DK and Leopard 2A7V feature hull add-on modules, but no roof armor, giving us an idea about the relative weight of both armor systems). The Stridsvagn 122 was used as demonstrator by KMW in the Greek tests, because it was considered superior to the German tank. If "D-1" would refer to the additional roof armor, why wouldn't it look like this for the "German model"/KVT? Given that the tank featured roof add-on armor... Also the term "Vorsatz-Modul" strictly translated would be "module that sits in the front", not "on top" as roof-mounted armor would do. You can try to contact Lindström, but given that he removed the original files and photographs from the armor tests from his website, I don't think he is allowed to answer your questions.

There are several authors stating/implying this and at least one photograph of the Leopard 2 turrets without armor inserts during the upgrade process. There are multiple possiblities how the protection might have been improved without increasing weight by a significant amount, also it is worth noting that we don't know the protection level against chemical energy rounds. Replacing steel with ceramics or using higher quality steel/DHS/THS could allow increasing the KE protection without affecting the weight, likewise altering the armor layout might help (using less NERA panels, but thicker ones with HHS capable of affecting APFSDS penetrators by a larger amount). There is a Russian book claiming that West-Germany tested armor arrays during the 1970s, which were more comparable to the T-72B's internal NERA array (i.e. each sandwich plate consisted of a thicker frontplate made of steel with higher hardness followed by only a very thin rubber sheet and steel plate), which seems to be more capable of defeating APFSDS ammo. If the Leopard 2's "B" technology armor follows another layout (comparable to the M1 Abrams' BRL-1 composite), then switching to this array-type at the same weight might improve protection against KE (for potentially loosing a bit of CE protection). Think about it this way: the tanks have already been ordered years ago, so if the manufacturer has already developed a new armor package that has finished testing, why not use it? The wedge-shaped add-on armor was already fitted to the KVT (most likely not identical to what later went into production, but in an earlier form) in 1989, it might have been already available in 1988. The TVM Min. and TVM Max. (which was used for some Swedish tests) were based on two Leopard 2A4 tanks from the eight batch and should therefore feature something like "D-1" base armor. All prototypes of the Leopard 2A5 had the "flat" side add-on armor modules, but all series production versions featured the wedge-shaped side armor. The add-on armor used on the Stridsvagn 122 seems to be identical to the one used on all series versions of the Leopard 2A5 and Leopard 2A6 tanks. That suggests the the changes to the add-on armor proposed by Sweden might have been adopted by all Leopard 2A5/2A6 users (Ingenieurbüro Deisenroth made apparently the add-on armor for all different 2A5 versions). My understanding - or my theory - is that to keep the costs down Germany at the time of the Swedish trials was planning to upgrade the Leopard 2 with armor of the "B" generation by simply installing add-on armor (D-2), which Sweden considered to be insufficient, hence the proposed Swedish model featured a significantly higher level of protection. However after the Swedish trials (or during them), a number of factors (for example the decision to downsize the Bundeswehr and completely dissolve the Bundeswehrkommando Ost, the cancelation of the PzKpfW 2000 tank project, budget decisions, data of Soviet ammunition becoming available to NATO, appearance of the T-90, etc.) lead Germany to change the configuration "German model" of the Leopard 2A5, to also include "C" and "D-1" generation internal armor arrays. As a cost-cutting or weight-saving measure these changes to the configuration also required to drop the add-on armor modules for the turret roof and hull, whcih are part of the "German model" in the Swedish presentation by R L. I agree with yellow most likely showing the Leopard 2 with "B" generation internal and "D-2" generation external armor. The graph shows five different colors, but there are five different armor technologies with multiple possible combinations options. I think we can agree that the purple/pink graph shows the "B" armor package, while the red graph shows the "C" armor package; so if yellow shows "B" + "D-2", where is the graph is the "D-1" generation armor package and where is "D-3". Is the blue area the "D-3" armor kit ontop of the "B" armor package or the "D-1" or "D-2" add-on kit on the "C" generation base armor? And what does the green graph show, "D-1" base armor plus "D-2" or "D-3" add-ons or maybe the "B" or "C" oackge with the "D-3" add-on modules? I think it seems clear that the Stridsvagn 122 is equal to the green graph based on the statement that it meet the required levels of protection at more than 70% of the places and that its hull armor managed to stop the 120 mm APFSDS round with 700 mm penetration. As I believe that the Stridsvagn 122 was made with the most advanced base armor available at the time (D-1), that would leaave the blue graph to show the "C" technology base armor + unknown add-on. It seems you misunderstood me to some extend, I never said, that the Leopard 2A4 from 1991 with (what I believe would be) "D-1" armor would provide a higher level of protection than the KVT ("B" baseline protection + "D-2" modules); that alone has more than 700 mm equivalent turret armor protection against KE, which would be physically impossble with the Leopard 2A4's armor thickness. I'd expect it to fall between the yellow and the red graph. I don't think there was any add-on armor in these armor tests. It was one steel plate, one composite armor module, two steel plates and a few other layers. Unless the add-on armor was somehow capable of stopping the LKE1 APFSDS by itself, I would have expected there to be two composite armor modules (one for the add-on armor and one for the base armor) in such a test. The Panzer 87 with Swiss 140 mm smoothbore gun is fitted with armor made for the Panzer 87 Werterhaltung program of 2006. Research and development for this armor was started by the company RUAG (owned by the Swiss government) in 1999. It has no relation to what Germany was offering in the 1990s and wouldn't have been tested against the LKE1 APFSDS. Thanks. These are great photographs, I've seen people making armor thickness estimates for the M1(A1/A2) Abrams for years, but nobody managed to make any actual photographs. Seems that I've understimated the armor thickness, but that was a result of the backplate. The measurement from the outside (where the backplate is not fully included) it shows a thickness of ~34-35 inches (860-890 mm). So the M1A1/A2 have the same armor thickness at normal (no slope), that the original M1 Abrams had with slope. Well, the Swedes got 50% protection mostly as a result of weakspots (gun mantlet, turret ring, roof) and including the turret side armor. Only the turret frontal cheeks are meant to protect against APFSDS rounds with 600 mm penetration at the 30° arc. The turret side armor protects only against 480 mm KE along a 20° arc (although it seems that the whole crew compartment is located behind the frontal cheeks when seen at 20° angle from the turret centerline). Patent DE3508053A1

Rheinmetall's strategy for Challenger 2 LEP in four words: "120 mm smoothbore gun"

Artists conception from Rheinmetall on how the MGCS might look: PL-01, is that you?

The Greek article on the trials is just two pages long and doesn't go into detail about armor protection other than saying that the Leopard 2A5 had the best, followed by the M1A2 Abrams and that the Challenger 2's armor was disappointing, being merely better than the Leclerc. The CR2 features improved roof armor over the Challenger 1, it should be better than the Leclerc and Abrams in this regard.

Both Rolf Hilmes and Frank Lobitz specifically mention that the base armor of the Leopard 2A5 was replaced with new inserts in "D" technology. During the Leopard 2A5 upgrade process, the turret structure of the Leopard 2A4 is cut open and new armor inserts in "D" technology are installed. For the last batch of Leopard 2A4 tanks Lobitz mention that the tank featured "improved armor protection" and at another place that it can be identified by the new light side skirts in "D" technology... adding one and one together and this leads to the last Leopard 2A4 featuring "D" technology armor. This photograph shows two Leopard 2 turrets (from the earliest production lots, as one can see by looking at the ammunition loading hatch) during upgrade to the Leopard 2A5 standard according to Rolf Hilmes. The armor insersts have already been removed, the location of the EMES-15 and the surrounding armor layout is being modified on the turret at the rear. According to Michael Scheibert, author for the (nowadays defunct) Waffen-Arsenal book series, the (first) Leopard 2A4 armor upgrade was weight neutral, i.e. there was no weight gain or loss (although I personally believe that there was some minor difference). The 56.6 tonnes figure is rarely used, but it has appeared in a quite a few articles on the Leopard 2A4 and a number of press releases (for example the company Ingenieurbüro Deisenroth stated in an article about the reveal of the Leopard 2 Evolution upgrade with AMAP armor, that the Leopard 2A4 used as basis for the demonstrator had originally a combat weight of 56.6 tonnes, which had to be lowered by removing the side skirts before the Evolution kit could be added to remain in the desired 60 tonnes weight limit). It isn't actually confirmed that this weight figure is related to the extremely rare Leopard 2A4 with "D" technology armor (only 75 made for the Bundeswehr of which only 1 still exists) or not - but unless the literature is wrong and the version with "C" armor is actually heavier than 55.15 tonnes, the 56.6 tonnes figure has to refer to the latest version by the method of elimination. In theory the Leopard 2A4 with "D" technology armor might also be heavier than 56.6 tonnes, I've never seen an actual weight value specifically mentioning that it belongs to the 75 tanks of the eight production batch. The Soviets adopted new armor arrays (mainly for the hulls of their tanks) at a much steadier rate, e.g. the T-72B was built with three different armor arrays within a period of just 5 years. West-Germany adopted the new (and more protective) Leopard 1A3 turret just 13 months after the new turret for the Leopard 1A2 had entered production. The M1IP version of the Abrams entered production four years after the M1 Abrams, yet it featured improved armor and a longer turret. So three years for a new Leopard 2 armor package developed at the height of the Cold War doesn't seem implausible. This image is from a set of documents delivered by Krauss-Maffei to Sweden and leaked as part of R. L.'s presentations. It shows the references for the armor packages (although it doesn't mention wether this means that the armor protection is comparable to the Soviet tanks or meant to resist rounds fired by these Soviet tanks). The 3rd generation armor package (which would be "D" technology based on the German naming scheme) was adopted in 1991, yet the Leopard 2A5 entered service in 1995. It was meant to compare to the (armor or firepower of the) FST (Future Soviet Tank), which was expected to enter service in the 1990s and feature a next-generation gun (various different calibers including 125 mm, 130 mm, 135 mm and 152 mm have been mentioned in different articles over the years). It appears that in fact both new armor packages for the Leopard 2A4 and the Leopard 2A5 were developed after the BMVg (German MoD) requested a higher level of protection back in 1984, which kickstarted the Leopard 2A5 development (a first prototype with add-on armor looking similar to the 2A5 being tested in 1986). Please note that there are three versions of "D" technology armor (D-1, D-2 and D-3). The Leopard 2A4 could use "D-1" inserts, while the Leopard 2A5 made for Sweden could feature "D-2" or "D-3" inserts. I don't think that Krauss-Maffei would choose this "table format" for displaying armor packages, if the "D" technology armor was only available as add-on modules. Note that the line "Pakete" (armor inserts) also contains fields for the three types of "D" generation armor. Also note that "Technologie-Kombination" means "technology combination" (implying that all types of add-on armor modules and base armor can be easily combined). It is indeed a very odd situation, I can understand your skepticism. I probably also wouldn't believe anyone saying that he has a classified source showing that a tank had a much higher level of protection than other people consider plausible. I can only say what I have seen and what I've heard. I don't think the M1A2 still has the same level of hull protection as the initial M1 Abrams. The British stated that the later has a protection was only 320 mm against kinetic energy penetrators (from the front?), while the M1A2 offered to Sweden reached 350 mm along the frontal arc (it could be a bit more directly at the frontal cavity, given that the weakest sectioon of the frontal arc is probably the side skirt area at 25-30°). The hull armor was upgraded with the variants M1A1/M1IP (there were at least weight demonstrators welded to the hull front of the M1E1). The hull armor of the Leopard 2 can be upgraded more easily, in the original models there even was a hatch to access the armor inserts (which was shut via bolts), only during the upgrade to the Leopard 2A4 this was shut by welding. In a Canadian Army maintenance facility, they have opened the hull armor cavity of a Leopard 2A4 with "B" armor package (the edges of the plates inside however are oddly soft compared to the rest of the photograph, they might have been added with photoshop): As for the weight increase and the corresponding increase in armor protection, there are multiple factors to consider. First of all, there are differences between both tanks, that shouldn't be ignored. The Leopard 2A4's turret front is about 15% smaller than that of the M1A1 HA, thus for an equal increase in armor weight, the Leopard 2A4 would require only a weight gain of 2.55 tonnes. The 1.45 tonnes that the Leopard 2A4 with "D" technology might be heavier (assuming the 56.6 tonnes figure is correct) than the earlier variants seems to fall a bit short of that, but the question remains wether a M1A1 has the same amount of (turret) armor weight per volume as the Leopard 2A4 with "B" or "C" technology armor. Given the larger frontal profile and the extensive side armor, it seems possible that the Leopard 2A4 has actually denser armor to start with (at least this was the case when comparing the Leopard 2 to the M1 Abrams). Another factor is the side armor: the Leopard 2A4 from 1991 features new light side skirts made of high-hardness steel, which supposedly provide the same protection level at a slightly smaller thickness than the previous type. Also there are unconfirmed rumors about the side armor at the frontal section being different; some Danish soldier claimed that the Leopard 2A5DK has thicker steel side armor than the Strv 122, which at least partly might be confirmed by the fact, that the latter had a slightly lower protection level against RPGs hitting at 90° angle than the Leopard 2 KVT during the Swedish tests. Compared to the M1A2, the Leopard 2A4 has a much larger gun mantlet, which probably wouldn't be able to reach the same protection level (and probably would also have a much lower weight than the main armor). The makers of the video game War Thunder measured the thickness of an early-model M1 Abrams using tape measures and an ultrasonic probe.They concluded that the backplate of the hull armor is 101 mm thick (excluding slope), which seems to be quite a bit. The Leopard 2 - at least on the turret - uses what seems to be a 40-60 mm thick backplate, thus more weight can be invested into special armor with a higher mass efficiency. Maybe the turret armor also follows this layout, at least the people from the War Thunder developer claim that the size of the special armor cavity is only 19.5 inches (I believe without slope). Assuming that the turret backplate is also 101 mm thick and knowing that the measured thickness of the turret frontplate was 38.1 mm, the total thickness of the M1 turret armor would be 634 mm or ~732 mm LOS from the front, which falls into the range of estimated armor thickness from various internet users. It is worth noting that the M1A2 turret in Sweden provided 600 mm protection vs APFSDS rounds along the frontal arc, the armor tested in Germany was however simulating a hit directly from the front (otherwise the armor would be way too thick). So there still could be a ~10% difference in armor protection in favor of the M1A2 (esp. considering that the armor package with DU might be slightly better). There is no doubt that the armor array survived a hit by a LKE1 APFSDS without being fully penetrated, which is why there are a few possible options: The armor might not be identical to the one adopted on the Leopard 2A4 production model of 1991 - however the armor was tested before the DM43 APFSDS was type qualified (which IIRC happened in 1994 or 1996) and it was offered as an upgrade option for users of the Leopard 2A4 with "B" generation armor, so that doesn't seem to be the most likely option. The Leopard 2A4 from 1991 might have a larger combat weight than assumed; it is a really rare variant and no user of the Leopard 2A4 seems to have ever upgraded their 2A4s to a version with "C" or "D" armor package (at least the side skirts have remained identical). The LKE1 APFSDS being a prototype mgith mean that it actually had a lower level of armor penetration than the DM43 APFSDS - but it probably was always superior to the DM33 APFSDS it was meant to replace (which apparently has ~480 mm at 2,000 m penetration). The Leopard 2A4 armor from 1991 could be highly optimized against KE, potentially sacrificing relative protection vs HEAT. The rumored inclusion of tungsten and titanium would support this, as this would be similar to the DU armor of the M1A2 (at least the SEP features titanium within its armor array). I dont think that is very accurate. I've seen a wide range of estimations for the M1A2's turret front (as low as "below 800 mm" and as high as 1,100 mm), yet no accurate measurements have ever been made. The M1A2 models use the same turret dimensions introduced with the M1IP in 1984; at this time 940 mm physical thickness would have been more than any other contemporary tank (T-72B, T-80U, Leopard 2 and Challenger 1 all having 800-870 mm physical thickness along the line-of-sight at most). How did you estimate the thickness? Did you keep in mind that the slope of the turret cheeks is assymetrical (left turret cheek is sloped more than the right). Also don't forget that this is 600 mm along the frontal arc, so it is achieved by the unsloped armor package already. While the M1A2 Abrams has a combat weight of 62.5 tonnes, the armor weight was likely not increased over the M1A1 HA (at 61.8 tonnes; the M1A2 adds a lot of additional parts to the tank that might explain the weight difference); this is about 3 tonnes heavier than the M1A1 when both tanks are fitted with the T158 tracks. There have been several statements from various sources hinting that there are more armor generations. When the Leopard 2A7 entered service with the German army, Jane's Defence Weekly stated that it is being protected by a "new generation" of armor in the turret and hull. According to Polish news agencies, Rheinmetall claims that the Leopard 2 turret with AMAP armor provides more protection than the Leopard 2A5 turret, but equal protection to the Leopard 2A7. There are also some mentions about certain exported tanks featuring "improved armor", although it is never mentioned what the point of reference is. It seems rather reasonable to assume that after the "D" technology armor from 1991/1995, armor development didn't cease. The Leopard 2A7V prototype presented at Eurosatory 2016 for example features a different hull add-on armor kit compared to the Stridsvagn 122 (similar thickness, but the size and location of the mounting screws is different). No, the entire armor array that stopped the LKE1 APFSDS was about 800 mm thick: 100 mm soft steel, 500 mm special armor, two layers of 100 mm soft steel. The APFSDS reached the third steel plate, so it defeated more than 700 mm armor. The Leopard 2 is said to feature some extremely expensive steel types, which provide high levels of protection. For example according to the company that provides the very few cast steel elements for the Leopard 2 tank, the cast steel has a hardness of 350-380 HB on the initial model and 380-420 HB on the Leopard 2A4 and Leopard 2A5. The turret shell of the initial model was made of HFX 130 steel with an average hardess of 380 HB; it seems likely that the Leopard 2A4 tanks with "C" and "D" generation armor use different steel with a hardness of more than 400 HB (note that on the photograph showing the Leopard 2A4 turrets being upgraded to the 2A5 standard, the outer steel plate of the turret structure of one turret is missing). According to an article published in the International Symposium on Ballistics by a German scients working for the Franco-German Institute in Saint-Louis (which is focused on military research), special combinations of high-hardness steel plates (probably as DHS or THS) can reach a thickness efficiency of 1.8 compared to RHS. DHS can reach a thickness efficiency of 1.78 accoridng to Hazell's Armour. Jane's Defence Weekly reported during the 1990s (or at least it claimed to have reported), that the Leclerc (contemporary to the Leopard 2A4 with "D" tech armor and the Leopard 2A5) uses THS with a thickness efficiency of 1.81 as part of its armor array. However DHS and THS are very expensive. Heavy metal alloys such as DU and WHA have also both shown a thickness efficiency larger than 1. Another factor is that the LKE1 APFSDS was still in development, the performance figure is estimated based on the actual 120 mm DM43 that was IIRC type-qualified in 1994 or 1996 (this also is a nice way to see that the armor array was tested in the early 1990s). The Leopard 2A5 requires swapping out armor inserts aswell, while requiring a modification of the armor layout at the gunner's sight, new hooks for the add-on armor modules and hinges for the new mantlet armor modules, a modification of the gun (with different trunion), modifying the optical channels of the sights and numerous changes not related to armor protection.

It seems that the British documents use values for protection along the full 60° frontal arc. The minimum thickness of the Leopard 2 turret cheek armor along the frontal arc is roughly 660 mm. 860/660*350 = 456 mm 860/660*420 = 547 mm That matches the current interpretation of this graph from the Swedish documents: Furthmore there is the statement about the M1A1 HA's DU armor providing 15° more protection than the Dorchester armor of the Challenger 2. Given that the former is believed to provide 600 mm protection vs KE along the frontal arc based on the Swedish documents (or about 660 mm from straight on assuming that the armor efficiency stays the same regardless of horizontal slope), this would put the Challenger 2 at 510 mm (560 mm head-on) vs KE. The protection requirement for the turret was armor equivalent to 500 mm steel vs KEPs (along the frontal arc?). Even more so, the Brits believed the M1 Abrams to feature turret armor providing 340 mm equivalent protection vs KE along the frontal arc. That would be equivalent to 392 mm vs KE from head-on. A CIA document puts the M1 Abrams' turret at 400 mm vs KE.

According to different German authors (Rolf Hilmes, W. Spielberger, Frank Lobitz) the base armor used on the last batches of the Leopard 2A4 and on the Leopard 2A5 is based on "D" technology. The original armor package for the Leopard 2 (in "B" technology) remained in production until the 96th vehicle of the sixth production batch; starting with the 97th vehicle of the sixth batch, the new armor kit in "C" technology was used. The original Leopard 2A5 prototype (the KVT) was based on a hull made in 1987 as part of the fifth production batch, hence it was made with the original base armor package, only the add-on parts made use of newer technology. Beginning in January 1991, the tanks of the eight production batch with new armor in "D" technology were manufactured. These tanks were manufactured at the after the late Leopard 2A5 prototypes (TVM 1&2 Max., IVT) were manufactured, for which the new generation of armor has been developed ("D" technology), hence they used this type of base armor. The Leopard 2A5 KVT was send to Sweden, because the newer Leopard 2A5 prototypes were still being tested in Germany, this is the reason for the "German model" using inferior armor compared to the configuration ordered by Sweden (which apparently used "D" technology base armor + add-on parts). The Leopard 2A4 tanks with "D" technology can be identified by the side skirts - they are identical to the ones used on the later versions including the Leopard 2A5, 2A6 and 2A7. (Leopard 2A4 with "D" type armor) The production model of the Leopard 2A5 tanks for the German army was created by mating Leopard 2A4 hulls from the last production batches (with armor in "C" or "D" technology) with turrets from the earliest production batches. The old turrets are used, because they require extensive rework during which the base armor is replaced with new modules in "D" technology. This actually means that some Leopard 2A5 hulls might be better protected than other. There are no add-on armor modules on the German Leopard 2A5 hulls, because it was scheduled for adoption at a later time, it would have been added simultaneously with a new turret with the 140 mm L/48 NPzK smoothbore gun, as this would already require a more extensive rework of the hull (for example modifying the ammo racks to be suitable for 140 mm two-piece ammunition). The Leopard 2A7V will be the first German version too feature hull add-on armor modules, although this might be "E" or "F" type armor. I haven't seen any texts, but a set of photographs of an armor array being tested. It consists of a thick steel plate, a large box labeled "Sonderpanzerung" (special armor), two further thick steel plates followed by a number of several other plates, some of which appear to be non-metallic. I was told that the thick steel plates have a relatively low hardness, but are used to simulate thinner plates of very high-quality (and very expensive) ballistic steel. There is no external armor module. In front of the armor array is a sign from the German WTD saying that this array is being tested against the LKE1 APFSDS at a range of 2,000 meters. The other photos show the three thick steel plates after the armor array was hit: one shows the exterior of all three plates, each showing the marks of the APFSDS penetrator. Another photograph shows the inner side of the three thick steel plates: two of them have been completely penetrated, while the other one has only a dent of the APFSDS penetrator. There is also a ruler/measurement rod, which suggest that the "Sonderpanzerung" is about 500 mm thick only. The steel plates are about 100 mm thick, but supposedly they are made of mild steel; the actual ballistic steel would be some fancy type of high hardness/triple hardness steel providing a much higher level of protection per weigth and thickness. I actually haven't seen any proof that this armor belongs to the late Leopard 2A4 tank, but I consider the source very trustworthy. This armor was supposedly offered during the early 1990s as a cheap upgrade option to several Leopard 2 users, who didn't want to pay for the more expensive Leopard 2A5 upgrade, which is why I believe this is the "D" technology armor. According to different authors, there are (unconfirmed) rumors about the late Leopard 2A4 armor featuring titanium and tungsten, which might be broadly similar in to the DU armor of the M1A1 HA (at least the M1A2 SEP uses titanium to allow improving the armor protection without increasing the mass of the armor considerably). It is worth noting that AFAIK only the Leopard 2A4 with "D" technology is actually heavier than the Leopard 2A4 with "B" technology, apparently by 1.45 tonnes (at least the weight 56.6 tonnes has been quoted for the late Leopard 2A4). The M1A1 HA upgrade is heavier, but might cover more surface area and might have initially lacked the titanium weight saving measure. I know that the "I have access to secret sources" argument is very weak, but the details about this armor come from a source that is located in one of the countries to which the Leopard 2A4 armor upgrade was offered during the 1990s. As it was never purchased by this country, the documents have only a low level of classification (IIRC every tank commander can access them). As far as I know it should be hollow, at least for the early version of the Leopard 2.

I don't think that it refers to mass of the special armor. Note that the following document seems to list the MBT-80 with "430 mm+" protection, while also listing the effective hull armor thickness of Centurion and Leopard 1 (implying that the figures for the other tanks might also be hull armor). In documents from 1969 and 1970, it is already mentioned that Chobham armor has a mass efficiency of above 1.0, so 430 mm steel-equivalent mass should provide a noteworthy larger amount of armor protection. It also would be odd to mix figures in milimeters with tons (for the applique armor) without even specifying that the milimeters is meant to be steel-equivalent mass.

I don't know, this is what I have read in another discussion on another website. As I said I don't own the book yet. I might have mistaken the values from a random discussion with a footnote from the book, which says that the Challenger 1 mounted armor providing "equivalent amounts" to 430 mm for the turret and 315 mm for the hull.

The yellow graph might correspond to the Leopard 2A4 with "D" technology armor (production start in 1991), not the Leopard 2A4 with "C" technology armor (production 1988-1991). I can say that the late Leopard 2A4 turret front with the latest armor ("D" technology) did survive a direct impact from the LKE1 APFSDS fired from 2,000 m distance without the projectile reaching the inner layers of the armor array. This round was later type-qualified as 120 mm DM43 APFSDS (given its 600 mm penetrator length and 1,740 m/s muzzle velocity, it should be able to penetrate about 600 mm of flat armor at this distance). The sources for this is classified, unfortunatley it cannot be shared without potentially getting some people in trouble.

The way the sentence mentioing this is phrased, the 480/340 mm are the actual protection achieved by the Challenger 1 tank with Chobham special armor. The 500/275 mm are the design goal from a time, when the Challenger 1 was still in development. If you read through this topic, there is a snipplet from a British report on the M1 Abrams (the M1 Abrams was considered as an alternative to the Challenger 1), which mentions that most of the initial tests with the "safe" ammo separation actually failed, apparently because the bulkhead was not strong enough to deal with the pressure in the split seconds before it was successfully lowered via the blow-off panels. Other than that, the Abrams' turret ammo storage increases the frontal profile while at the same time requiring additional armor at the turret sides (due to the fact that such a large quantity of the total ammo load is located within a single place; one does not want a single RPG to take away essentially the complete ammo loadout of a MBT). The British - and the Germans - believed that putting more ammo in the well-protected frontal section of the hull was desirable. This is from the late 1970s, there was still quite a lot of development going on before the Shir 2 tank became the Challenger 1 (one difference being the improved turret armor of the latter), while NATO didn't know much about the Soviet tanks. The hull of T-64 and T-72 were believed by the British to feature only 100 mm steel sloped at 68.5° as frontal armor (which is 272 mm steel along the line-of-sight), a major underestimation. The statement about the Leopard 2's turret armor being worse than the Chieftain with Stillbrew is directly focused on frontal protection (i.e. when being hit straight on) against kinetic energy penetrators of the turret front. The Leopard 2 apparently has 400-450 mm (depending on location), with the gun mantlet potentially being worse armored (~350 mm; at least that seems to be the conlcusion of the analysis done by @Laviduce) - so the Chieftain with Stillbrew seems to be quite a bit better armored. The 120 mm DM53 APFSDS round did not exist at the time of the Swedish tests and certainly wasn't delivered to Sweden. The photograph most likely shows a test projectile made only for the evaluation. The data for the Leopard 2 tanks apparently comes from Krauss-Maffei and likely does not reflect what Sweden was able to test (it would be very odd to let Sweden fire its APFSDS rounds and shaped charges at every possible armor package ever made for the Leopard 2, if they are only interested in the latest one(s)). The extract from the book regarding Chieftain''s armor already shows that the British underestimated the performance of Soviet rounds, it says that (in 1981) the penetration of the T-72's 125 mm gun was estimated to be 420 mm for steel penetrators and 475 mm for tungsten penetrators point-blank at normal (aka 0 meters, 90° impact angle). The United States also underestimated the performance of the Soviet 125 mm gun and ammunition, one could say they did that to an even greater extent.

Eleverbara systemets - elevation system, Vapensköld - gun shield (mantlet), Hylskorg - basket for the propellant stubs, Krugasejektor - fume extractor, Backstycke - back part of gun (breech block, etc.), Kil - wedge lock, Vappenvagga - gun cradle, Framförare - the opposing actor to the recoil brake (don't know what the exact term is in English), Rekylbrom - recoil brake The Vappenvagge should include the trunion, but also the other parts of the cradle, at least if the definition is identical to the German one. I.e. everything orange: (ignore the spelling mistake) (Gun cradle of the M256 gun) AFAIK it is all calculated based on the LOS thickness at these tangles and the performance data delivered by the tank manufacturers without any simulation of materials. The graphs on this page are not from Sweden, but part of the documents delivered by Germany (that's why the description of the table is in German). The data should be valid for the complete vehicle surface at the relevant angles.

"12 cm kanon strv 121/122 - Skjuttabeller" by the Försvarets Materielverk (i.e. the official firing tables and technical manual of the 120 mm gun of the Swedish army). The title of the document suggests that the data would be largely valid for both the Stridsvagn 121 (Leopard 2A4) and the Stridsvagn 122 (Leopard 2A5), but the drawings and total weight suggests that the weight data is taken from the Stridsvagn 122. But the 110 kg was wrong, I read the value from the wrong column/line by accident. It might be a lot heavier, the trunion with supports is listed as 595 kg. The AVDS-1790 was a much older design that was only used for the M60, because the United States originally focused on different projects (mainly the T95 medium tank) and only went back to using the AVDS (which already had been used in slightly different versions in the M47 and M48 Patton tanks) after these ended unsuccessful. The overall situation is a bit worse considering that the United States were using SAE gross horsepower at the time (i.e. they measured the maximum possible power output in the baseline configuration by excluding any factors such as cooling fans, that would result in a loss of power), while Germany was using DIN-PS according to the standard DIN 70020. When the US switched from SAE gross horsepower to SAE net horsepower in 1972, the power output of all advertised cars was significantly reduced (e.g. the Chrysler 426 Hemi famously engine had an output of 425 gross hp, but only 350 hp net). The AVDS-1790 is however a robust design that had a lot of unused potential, as seen by the later variants (with up to 1,200 hp net horsepowers) used by Israel and others. That is the third revision. The original M60A1 in SteelBeasts had 633 mm at the turret front and 400 mm on the mantlet, because the author assumed that the 254 mm was the physical armor thickness before slope... http://www.tank-net.com/forums/index.php?showtopic=26578&hl=m60a1#entry618626 After that there was an intermediate version, still with way too much armor: But the Leopard 1A3 is also overrated by Steel Beasts... The Swedish protection analysis is focused on the crew compartment only; everthing outside the crew compartment is not analyzed. I know what you mean with the "slit" in the armor protection, but unfortunately I don't have an answer to that question. Maybe this is accurate and a result of how the armor elements are arranged within the array, but it also could be a minor error in the calculations. That might be related to the timeframe. The document is from 1969/1970, when the only 115 mm APFSDS NATO knew off had a steel penetrator with no tungsten carbide. It easily shattered when hitting spaced or sloped armor, while having overall rather low armor penetration (200-240 mm at 2,000 meters against flat steel armor). However the Soviets already had the 115 mm BM3 with tungsten-carbide slug at the tip of the steel penetrator, capable of penetrating 270 mm RHS at the same distance - this was AFAIK the first type of 115 mm ammunition accepted by the Soviet Union, but it was expensive and not exported, so NATO only knew about the all-steel penetrators.

This is a snipplet from "Challenger 2 Main Battle Tank Owners' Workshop Manual: 1998 to Present" by Lt. Col. Dick Taylor of the RTR. Apparently the M1A1 HA's DU armor results in about 15% better protection against APFSDS ammunition compared to the Challenger 2, but offers a lot lower protection against HEAT munitions. Given that the M1A1 HA's turret appears to have approximately 600-660 mm vs KE (estimated 30° arc and direct from the front), that would put the Challenger 2 at 510-560 mm vs KE (this figures would match the earlier documents form the Challenger 2 design phase asking for 500 mm vs KE on turret and hull). The Challenger 1 was designed to reach a protection level of 500 mm vs KE on turret and 275 mm vs KE on the upper hull front, but according to a footnote in the same book reached only 480 mm vs KE on the turret and 340 mm vs KE on the hull. The Leopard 2 was apparently not only offered with the B armor configuration (as tested in the UK), but it was at least proposed with the C and D armor generations aswell (protection level of the latter armor type not being disclosed to the UK). It seems that the text on the right mentions protection figures in milimeters for the Leopard 2A4 with Type B and Type C armor configurations, but that is unfortunately cut off. The Leopard 2A4 (with Type B armor) was rejected for its poor armor, worse than the Chieftain with Stillbrew vs KE. Does anybody have this book? I wonder if it is worth the read, because other snipplets I've seen seem to feature quite a lot of bias (i.e. tests of Challenger 2E in Greece).

The weight of the gun trunion of a Stridsvagn 122 (Leopard 2A5) is 110 kilograms including the mounting supports. The MB 838 CaM-500 has a weight of 1,950 kilograms. R. P. Hunnicutt lists the weight of the the M60's AVDS-1790 at 4,700 pounds dry (in case of the M60A1 and M60A2) and at 4,900 pounds dry (for the M60A3). That equals 2,132 kg and 2,222 kg respectively. According to "World War II Ballistics: Armor and Gunnery", the BR-412D can penetrate 235 mm of armor steel at 100 meters distance. Adding differences in criteria and steel hardness to this makes it rather possible that it could penetrate 240 mm armor steel at some ranges. But it seems US protection data is based on the BR-412B round with worse performance tested against cast armor only (at least the source is named "TACOM Ballistic Design Data 100 mm APHE BR-412B vs Cast Steel Armor"): so the hull armor protection might been under-estimated unless the US somehow thought that rolled steel plates with similarly low ballistic performance as the soft cast armor used for the turret was desirable. The claimed reduction betwen 5-15% reduction in protection is valid for 260-280 HB steel, not the 220-240 HB (which turned out to be only 210 HB during tests of a M47 Patton tank in Yugoslavia). Given that the US military used some of the softest cast armor and that even American authors like R. P. Hunnicutt criticized the poor quality of this steel, it seems likely that it would be closer to the 20% reduction in protection mentioned by German and Swedish sources. Yes, the M60A1 should be able to survive being hit by a 100 mm AP at some places of the turret front, specifically at the better sloped parts - but not everywhere... and thats what matters. The 50% metric somewhat makes sense, it seems to be the standard used by the US military based on numerous other documents. The BR-412B however is an odd choice. Never said it was equivalent, but similar protection when seen directly from the front. The M60A1 has much better hull armor, better turret side and rear armor, arguably a thicker mantlet and it has a larger protected frontal arc. But when seen directly from the front, the protection difference appears to be negible. The Leopard 1A3's turret was apparently tested against 90 mm HVAP ammo with tungsten-carbide core (West-Germany never used simple APCBC for the 90 mm guns of Patton and KaJaPa), which in terms of raw penetration actually outmatches 100 mm AP(CBC/HE) rounds by quite a bit, but may or may not be more suspectible to damage by spaced armor. In general spaced armor was very effective against older ammo, specifically against bullet-shaped rounds with spin-stabilization. The UK was happy, that the L15 APDS for the L11 tank gun of the Chieftain lost only 20% of its penetration against spaced armor arrays (after optimizations), while US tests showed that adding a 1/2 inch thick steel plate spaced in front of a 3-4 inches thick steel target could increase the protection against 90 mm M304 HVAP rounds dramatically (reducing the maximum range at which the armor can be penetrated by 1.500 to 2,200 yards depending on angle). Negative. First of all, the measure point is very close to the gun mantlet and gun mounting mechanism, which might be included at this very specific point. Cast turrets have variable thickness, so seeing one specific point having a certain thickness doesn't say anything. Aside of that, the slope won't be enough to reach 300 mm or more. The M60A1's turret front is ellipsoid, the angle of slope is varying by quite a lot. Close to the front of the turret, it is about 45° in the horizontal plane; when moving away from the center of the turret, the physicial armor thickness is reduced and the slope increases up to 60°. The right turret cheek, where the measurement was made, has a much less dramatic slope in the vertical plane; it reaches only up to 16° close to the commander's hatch and is only 10° close to the gun mantlet. The slope in the horizontal plane is varing between 4° (though the 4° is directly next the gun mantlet) and 57° (close to the commander's hatch), with the turret at the location of the measurement point being sloped at something between 44-50°. That puts LOS thickness at 261-290 mm and this value might be the result of the mounting mechanism for the gun being nearby. You keep forgetting that the 254 mm LOS thickness is the official figure used by the US Army in its internal documents. There is no logic behind prtending that the M60A1 has 300-350 mm KE protection at the turret (with ~400 mm mantlet), given that the US Army itself says that this is incorrect.

Do you mean the same "physical measurements" mentioned by heretic88 about five pages ago, which only focus on the gun mantlet, assume that it is completely made of armor-grade steel and not hollow at all? That's not reliable, just like the "solid titanium trunion of the Leopard 2, which doesn't exist. I've never seen any measurements of the actual M60A1 turret frontal armor aside those mentioned in the Soviet reports. The turret cheek armor seems to be ~100 mm thick at most (not accounting for slope), just as written in the Soviet reports. The weight difference between the turrets is much less than 10 tonnes. Add to this different profiles + armor technology (cast steel is less effective than normal RHS, spaced armor formed by rolled steel plates is more effective than RHS) and you got your explanation. Because in reality steel hardness and normal distributions in protection and penetration performance matter. The BR-412B and BR-412D with their blunt-shaped tips managed to retain most of their performance against sloped armor. The upper hull front of M48 Patton (110 mm at 60° = 220 mm LOS) was vulnerable to blunt-tipped versions of 100 mm AP rounds, when the impact velocity was in the range 880-900 m/s. The M60A1's hull armor is thinner but slightly better sloped (228 mm LOS). This is a ballistic limit according to Soviet criteria, meaning that 75-80% of all rounds will manage to penetrate the armor at this velocity. From the US perspective - caring about the protection - another criteria would be used, as you don't want to stop only 20-25% of all rounds at the desired range, but a reasonable amount (75-100%). That is why the ranges for protection are larger than the ranges for penetration of the same target in certain instances. Steel hardness was changed in 1978 for the M60A3, the M60A1 production ended around the same time. Most likely all M60A1 tanks were made with the softer steel. The Soviets (for most of their tanks, but the T-80 is apparently an exception) and the British used cast steel with a hardness of 260-280 HB, which supposedly was 5-15% weaker than RHS according to Soviet sources. German sources say that cast steel was "up to 20% worse" (20% more armor required to reach the same protection level) than RHS, similar statements are made by Sweden (cast steel being 10-20% worse than RHS). The Leopard 1A3 as mentioned by Wiedzmin uses steel plates with a hardness 301 HB and 370-410 HB for the frontal armor, up to 490 HB for the side armor plates and 260-300 HB for the roof armor. So there is quite a significant difference. The Chieftain was designed with a 45° frontal arc (±22.5 degrees), the M60A1 wasn't. Its armor relied much more on slope in the horizontal plane, very similar to the welded turrets of the Leopard 1 and Leopard 2K/PT. IIRC it was designed with a protected frontal arc of 30° (±15 degrees) or smaller. As Wiedzmin already stated, the Soviet reported that the "mantlet and cradle" provide protection against spall and bullets only, while not stating anything about the mantlet surviving 115 mm APFSDS rounds. You keep beating the same statement and ignore the fact that the same article from Andrei actually lists the gun mantlet as a weakspot!  So the Soviets, who actually captured a M60A1 found the mantlet to be badly armored, but they must be wrong, because someone on WarThunder forums measured the exterior (!) without knowing anything about the composition (RHS vs mild steel, hollow or solid) of the mantlet... And btw. that the turret front at 0° could be penetrated "at a close range" by 100 mm, 122 mm and 115 mm projectiles doesn't mean that it is immune to these and also doesn't mean that this range is identical for all these rounds.

The M60A1's turret is 200-254 mm thick cast steel with a hardness of 220-240 HB, that isn't going to provide 350 mm protection vs KE... According to Soviet evaluations of captured M60A1 tanks (probably gained via the Middle East) the frontal turret armor thickness ranges from 150 to 180 mm thick armor sloped at 22 to 30° in the vertical plane or 95 mm sloped at 35° horizontal and 55° vertical angle in front of the rangefinder. That is less than 220 mm of cast steel armor, which then again will provide 10-20% less protection than rolled armor steel.

RE: Leopard 1A3 turret armor... we discussed this already. It provides similar protection to the M60A1 turret (unless you believe SteelBeasts' incorrect older armor schemes).

Armor protection... Casting a turret is a lot easier, if you have the facilities to do so (which West-Germany had).

The there were tungsten and DU versions of the XM827 during development, but the DU version was prefered in the end (still canceled in favor for the M829 though). Likewise the US Army tested WHA and DU versions of the XM833. The article from the ARMOR magazine doesn't mention any materials, but it also includes one mention of the M735A1 (with DU penetrator). At the time, DU alloys could probably achieve better performance, but the 120 mm DM13 should be better than the M735 APFSDS and its M735A1 sub-variant, simply based on physics. It is availabe on the website of the German patent office, the European patent office, Google patents and many more https://worldwide.espacenet.com/publicationDetails/biblio?CC=DE&NR=2234219C1&KC=C1&FT=D# Actually it seems that modern tungsten heavy alloy penetrators are usually made with a slightly smaller tungsten content, in some cases as low as 90%. This way it is possible to create alloys with more ductility and/or strength.

https://www.janes.com/article/84530/turkey-signs-altay-mbt-serial-production-contract-with-bmc https://www.defensenews.com/land/2018/11/13/success-of-turkeys-indigenous-altay-tank-in-question-over-foreign-involvement/

The data used by Warthunder for the M735 is simply wrong. It is not possible for the M735 to penetrate the same amount of armor as the DM13 APFSDS at the same distance, given that penetrator length is essentially identical (~313 mm vs 315 mm), but the muzzle velocity and length-to-diameter ratio are in favor of the 120 mm DM13. An older article published in 1982 in the US ARMOR magazine suggests that the XM827 (German 120 mm DM13) has a 20% larger penetrator mass and was able to defeat all targets during the 1976 gun trials by NATO at longer ranges than the M735 (the M735 failed to penetrate some targets). Given the higher drag of the DM13, the M735 might be able to reach the same level of armor penetration at ranges greater than 4 kilometres (assuming deceleration stays constant up to this distances), but the 105 mm rifled guns M68 & L7 weren't considered accurate enough (neither was the 120 mm Rh 120 L/44 firing 120 mm DM13 ammunition). The layout of 120 mm DM13 is identical to a patented design from 1972. Patent drawing from patent DE2234219, registered on 12th July 1972. They certainly couldn't take design aspects from other APFSDS ammunition which didn't exist at the time. AFAIK the table posted earlier was made by another internet user, who based it on a (de)classified report. He might have made some error when entering the numbers from the paper into the computer, because the DM13's penetrator diamter is listed as larger than the actual diameter of the sub-projectile, which is physically impossible. The penetrator diameters for the L15 APDS, the L52 APDS and the 110 mm APDS are all smaller than the projectile diameter - just as expected. The weirdly shaped ballistic cap is in fact a windshield and a very normal design. Several other APFSDS rounds from NATO and the Soviet Union (among them the L23A1 APFSDS, Lekalo and Mango) use the same method to connect the windshield to the penetrator. The penetrator design and working mechanism is not similar to the Soviet 3BM-15 APFSDS and its sucessors. The Soviets used very brittle tungsten-carbide cores, which were shaped like bullets and embedded into the steel, because they would break otherwise. The tungsten-carbide tips would break off when hitting sloped armor or become damaged when penetrating spaced armor, which significantly reduced the performance of Soviet APFSDS. That is why the tungsten-carbide core was later moved to the rear of the penetator to deal better with spaced and composite armor arrays. 3BM-26, the tungsten-carbide penetrator is located in the fin-section. The DM13 APFSDS uses a penetrator made of WHA; the patent from 1972 suggests that 95% tungsten, 3.4% nickel and 1.6% iron would be desirable. The steel sheat is only added, because of the low yield strength of the WHA, which breaks apart when hitting (highly) sloped armor. The steel sheat apparently doesn't extend over the frontal (separate) section of the penetrator, because the tip always breaks off when impact sloped targets. Furthermore this layout was found to be advantageous against multi-plate armor arrays, as the larger frontal portion would result in a larger hole, through which the main part of the penetrator could travel without being damaged.