By the middle of the last century, the development of tank armament reached its peak in the field of calibers. In our country and abroad, several models of heavy tanks have appeared, armed with 152 mm guns. Attempts were made to install more serious weapons on a tracked armored vehicle with a turret, but they were unsuccessful. Moreover, already in the sixties, the military and tank builders realized that 152 or 155 mm guns were even redundant for a modern tank and therefore all modern vehicles are equipped with 120 or 125 mm guns. Nevertheless, from time to time there are projects concerning larger caliber guns. So, in the late eighties at the Leningrad Kirov plant was created an experimental tank "Object 292". An armored vehicle based on the T-80 tank carried a new turret with a 152-mm rifled cannon. However, a number of technical and economic reasons prevented the project from progressing further than testing the first prototype.
"Object 292"
NATO cannons
Around the same time that the Soviet Object 292 was being created, several European countries were discussing the possibility of developing a new weapon that would be the same for their tanks. As a caliber, both the usual 120 millimeters and the more solid 140 millimeters were considered. It is noteworthy that the result of the negotiations was a rather interesting approach to the creation of new guns. According to a memorandum signed by the United States, France, Germany and Great Britain, all countries could develop their own tank guns, but at the same time the parameters of the ammunition that were uniform for all were negotiated. In addition, the dimensions of the breech part of the barrel, some of the nuances of the chamber design and the parameters of the propellant charge were standardized: pressure in the barrel bore, etc. In other words, the international agreement implied the development of several new guns, designed for a single standard shot. The first standard ammunition was the APFSDS armor-piercing feathered projectile.
In the late eighties, it was planned that the new guns, created under the FTMA (Future Main Tank Armament) program, would become the main armament of NATO countries' tanks. The first such tanks were supposed to go to the troops approximately at the beginning of the XXI century. From the United States, several companies participated in the creation of NATO's new guns, including Rockwell and Lockheed. In the UK, a similar task has been assigned to the Royal Ordnance Factory Nottingham and several related businesses. France and Germany were represented in the program by GIAT Industries and Rheinmetall, respectively. In the course of research and development work, all participating firms studied a variety of issues. At the same time, the greatest attention was paid to studies on the installation of new 140-mm guns on existing tanks. For example, the German Rheinmetall tried to mount its gun on the Leopard 2 tank.
USA, ATAC project
The result of the work of American engineers was the ATAC (Advanced TAnk Cannon) complex, which consisted of an XM291 smoothbore gun, an XM91 automatic loader and a number of related equipment. In the future, this complex was planned to be installed on the upgraded M1 Abrams tank in the course of the next work to improve it. For this reason, a CATT-B (Component Advanced Technology Test-Bed) test bench was created to test the new gun. The CATT-B was a significantly modified M1A1 tank chassis with new suspension, electronics, etc. Until the end of work on this stand, the XM291 cannon was installed on a stationary unit and on the modified turret of the Abrams tank.
The XM291 gun was a 140mm smooth-bore tank gun with a separate cartridge case. The barrel was equipped with a heat-shielding casing. With the new 140-mm split shot, the muzzle energy of the XM291 cannon was approximately double that of the 120-mm M256 gun installed on the latest American tanks. At the same time, thanks to the use of the original design of the cradle and recoil devices, it was possible to provide a solid weight saving. The larger caliber gun was 91 kilograms lighter than the old M256. For unification with the existing tank guns, the XM291 was equipped with a removable barrel, and the breech design made it possible to replace the 140-mm barrel with a 120-mm one with corresponding technical and tactical consequences. Thus, the XM291 cannon, if necessary, could use both new powerful ammunition and old ones, available in sufficient quantities.
According to NATO standards, the gun ammunition was planned to be placed outside the fighting compartment, in the turret aft niche. The XM91 mechanism, created at the Bennett Laboratory of the Ground Forces, had the ability to automatically select the desired projectile from the ammunition rack and feed it to the gun. For greater safety of the crew, the shell and the sleeve were fed to the gun through a small sleeve in the armor wall between the fighting compartment and the stowage. At the same time, during the ramming, the projectile was additionally covered with a metal curtain. During tests, the XM91 autoloader showed a good pace of work - it provided up to 12 rounds per minute. In the ammunition rack, the size of which corresponded to the aft turret niche of the Abrams tank, it was possible to place up to 22 rounds of 140 mm caliber or 32-33 rounds and 120 mm caliber shells.
In addition to the gun, automatic loader and related equipment, three variants of shots were created specifically for the ATAC complex. All of them were equipped with a single cartridge case with the same powder charge. Structurally, the gunpowder sleeve was an enlarged sleeve for 120 mm guns. The ammunition nomenclature for the XM291 looked like this:
- XM964. A subcaliber armor-piercing projectile;
- XM965. Cumulative fragmentation armor-piercing;
- XM966. A training projectile that simulates both types of ammunition.
As of 2000, the ATAC gun complex was being tested. A little later, representatives of the American military department joined the development firms. Nevertheless, until now, the XM291 gun remains a purely experimental model. While testing it, some technical problems were revealed, such as too much recoil energy. Apparently, work on improving the gun continues to this day, but with much less intensity. The start of mass production was postponed several times, and at present there is no reason to expect the rearmament of American tanks. Probably, American armored vehicles in the near future will be equipped with 120 mm guns, and the new 140 mm gun will remain an experiment. In any case, back in the middle of the 2000s, funding for the ATAC project was greatly reduced.
United Kingdom
In 1989, Britain began two programs at once to develop promising 140-mm guns. One of them was carried out by the Defense Research Agency (DRA), the other by Royal Ordnance. It is noteworthy that in the early stages the second project was an initiative of the developer company and did not have government support. Regardless of the peculiarities of its beginning, both projects were proceeding at a good pace and already in the early nineties the first tests were carried out.
Both British-designed 140mm cannons were similar to a certain extent. This was affected by the agreement on standard ammunition. However, there were also noticeable differences. First of all, the designs of the recoil devices were different. According to reports, the DRA took the path of increasing the degree of unification of the new gun with the existing ones, and Royal Ordnance tested a new system. The general layout of the barrel, such as the presence of a heat-shielding casing, a post-shot purge system, the ability to quickly replace the barrel, etc., was the same for both guns. As far as is known, both British design organizations worked on their projects of automatic loaders, but they did not reach testing.
In 1992 and 1993, the 140-mm DRA and Royal Ordnance guns were tested, respectively. The firing was carried out with a standard APFSDS projectile. The total number of test shots exceeded two hundred. In the course of these tests, the advantages of the new weapons were revealed. First of all, an increase in armor penetration was noted. The 140 mm cannon, under the same conditions, penetrated 40% more armor than the existing 120 mm guns. Calculations showed that with a change in the material of an armor-piercing projectile, an additional increase in its penetrating qualities is possible.
British advanced tank armament mounted on the Centurion chassis
Nevertheless, during the tests, the alleged problems of the new guns were confirmed. Due to the increased energy of the propellant gases, the recoil has increased significantly. This led to the fact that both British development firms were forced to admit the insufficient effectiveness of recoil devices. It is worth noting that the parameters of the recoil of the guns made it possible to install them on promising tanks, developed taking into account new loads. However, there was no talk of modernizing the existing technology. The use of new guns on existing tanks threatened to damage structural parts of both the tank itself and the gun.
The result of testing both guns was a large amount of information, as well as a recommendation to continue work on this topic, but taking into account the requirement for installing guns on existing tanks. DRA and Royal Ordnance did not have time to actively engage in project updates. The fact is that after the collapse of the Soviet Union, the British command lost interest in new tank guns. The generals considered that in the near future there would definitely be no major tank battles and 140-mm guns were not needed. In turn, in the course of possible military conflicts, the existing tank guns of 120 mm caliber will be sufficient. Work on the British 140mm cannons slowed down at first and then stopped.
Germany, project NPzK-140
Unlike the British, the German designers from the Rheinmetall company immediately took into account the possibility of installing a new gun on the existing Leopard 2 tanks. At the same time, almost immediately after the start of the development of a new cannon, called the NPzK-140, it became clear that this would require a complete redesign of the tank turret. This need was due to both the calculated dimensions of the gun itself and the placement of a newly designed automatic loader. However, the creation of the new tower was postponed indefinitely: Rheinmetall decided that it was necessary first to complete all work on the cannon and only then to make the tower so that it would not have to constantly make adjustments to its design.
At the final design stage, the NPzK-140 gun was a typical tank gun, differing from others only in caliber. At the same time, several original solutions were applied in its design. For example, to ensure compatibility with the most convenient version of the automatic loader, the gun was equipped with a bolt with a vertically falling wedge. Also, the ejector of the gun had to be significantly redesigned and equipped with new recoil devices. The last task turned out to be one of the most difficult. Due to twice the energy of the powder charge of a standard shot, the recoil has increased significantly. But the chassis of the Leopard-2 tank, which in the future could be equipped with a new cannon, was not adapted to such loads. Nevertheless, the Rheinmetall designer eventually managed to reduce the calculated return to acceptable values.
Despite some success in the design business, the new 140mm NPzK-140 gun never went into production. At the beginning of the 2000s, a test bench and six copies of the gun itself were made. Tests of these guns went with varying success, but in the end the project was closed. NPzK-140 in its current state was considered inconvenient and unfinished. Not wanting to spend money on fine-tuning a new weapon, the German military chose to refuse the order. Some of the developments on this project, primarily of a technological nature, were later used to create the Rh-120 LLR L / 47 gun.
France
American, German and British projects of tank guns of 140 mm caliber were the most successful and reached the testing stage. In the remaining state party to the FTMA program, France, things were a little worse. So, the French company GIAT Industries, experiencing a number of technical and technological problems, eventually abandoned the creation of its own weapon. However, she took an active part in other projects and helped British and German businesses. In recent years, there have been rumors about the resumption of the French project, which now has old goals: to create a new weapon for promising European tanks. Despite the existing developments, full-fledged news about this project is unlikely to appear in the near future.
Outside NATO
Simultaneously with the USA, Great Britain, Germany and France, other countries that are not part of the North Atlantic Alliance became interested in the issue of increasing the caliber of tank guns. The motivation was exactly the same: an increase in caliber promised a large increase in basic combat qualities, and this advantage more than covered all fears about the high cost of development and construction or technical problems associated with high energies of the shot.
Switzerland
Interestingly, Swiss engineers from Swiss Ordnance Enterprise (SOE) began developing their 140mm cannon a little earlier than NATO countries. Apparently, Switzerland was counting only on its own strength and, seeing foreign progress in this direction, decided to also start a similar project. The construction of the Swiss cannon began in the mid-eighties. It should be noted that when developing a new tank gun was not considered as a full-fledged weapon for promising and modern tanks, but as an experimental model for determining the shape of the gun and testing new technologies. Nevertheless, even with such views, the possibility of mounting a new gun on Pz 87 Leo tanks (licensed Swiss-made Leopard 2) was taken into account.
There is information that the Rheinmetall Rh-120 gun, which was originally equipped with the Leopard-2 tanks, was taken as the basis for the new 140-mm tank gun. For this reason, the main features of the new cannon resemble the original Rh-120. At the same time, several solutions were applied to reduce recoil. Several years before foreign projects of similar guns, Swiss designers not only equipped their gun with new recoil devices, but also used a muzzle brake. The latter consisted of several rows of holes near the muzzle. According to some sources, muzzle brake efficiency exceeded 60%. In addition, due to the location of its holes at some distance from the muzzle, more efficient use of powder gases was ensured, since after passing through the brake holes, the projectile continued to receive energy from the gases for some time.
For the new gun, it was planned to create several types of separate-case ammunition, but the main one was the armor-piercing sub-caliber, for use with which the propellant charge was optimized. The burnable sleeve contained about ten kilograms of gunpowder. In addition, about five kilograms were attached directly to the projectile. Thus, in a separate-cartridge case, the propellant charge was divided into two parts. It was assumed that in cumulative or fragmentation shots, only a charge placed in a cartridge case would be used. Swiss-made ammunition had a serious difference from the shots described in the agreement between the NATO countries. Their sleeves were shorter and larger in diameter. According to the official data of the SOE company, in the future, if necessary, it would be possible to change the design of the cannon chamber and the shape of the casings for unification with NATO shells.
All technical solutions aimed at reducing the recoil momentum ultimately led to the possibility of mounting a new 140-mm cannon on the Leopard-2 tank. However, at first the tests were carried out on a special stand. The new Swiss cannon fired for the first time in the summer of 1988. At the same time, all the necessary data were collected and some modifications were made to its design. By the fall of next year, an experimental vehicle with an updated turret and a new 140-mm cannon was assembled on the basis of the Pz 87 Leo serial tank. During the firing on the stand and in the armament of the tank, the new gun showed more than interesting results. For example, from a distance of a kilometer, a sub-caliber projectile developed for it pierced up to a meter (!) Of homogeneous armor.
Despite successful tests, the new gun did not go into production. The reason for this end of the project was the high cost and complexity of the gun, as well as the lack of prerequisites for its introduction into service. In the early nineties, all European countries, as a result of the collapse of the USSR, reduced defense costs and the purchase of new weapons. The Swiss project of a 140-mm tank gun added to the list of works closed as unnecessary and expensive. According to reports, over the next years, prototype guns were used in various test programs, but it was emphasized that this is a purely experimental weapon and Switzerland does not intend to use it for military purposes.
Ukraine, gun "Bagheera"
In the second half of the nineties, a country from which such work was unlikely to be expected joined the creation of promising 140-mm guns. The Kiev Artillery Armament Design Bureau developed the 55L Bagheera high-power tank gun. It is argued that this weapon can be installed on any tank of the latest models of Soviet, Russian or Ukrainian production and significantly increases its combat qualities.
The available technical information about "Bagheera" is limited to a few figures. It is known that with a barrel length of seven meters (50 calibers), the 55L gun is capable of accelerating a seven-kilogram sub-caliber projectile to speeds of the order of 1850-1870 meters per second. The declared armor penetration is up to 450 millimeters at a meeting angle of 60 degrees. The firing distance was not specified. From the official data of the Artillery Armament Design Bureau, it can be concluded that at least two types of shots have been created for Bagheera. It is possible to fire with armor-piercing sub-caliber or high-explosive fragmentation shots of separate-sleeve loading.
There is no information about the tests of the 55L "Bagheera" cannon. From the photographs on the official website of the developer organization, one can draw a conclusion regarding the manufacture and installation of an experimental gun on a test bench. There is also no information about the purchase of the weapon. Probably, over the past years, "Bagheera" has not interested potential buyers.
Caliber and feasibility
As you can see, all projects of tank guns of the new 140 mm caliber faced the same problems. First of all, this is a super-powerful recoil, which could not be fully compensated for using old developments. Of course, in the practice of tank building, more serious calibers with appropriate recoil rates were also used, but all the new guns were intended to modernize the existing equipment, which was simply not designed for such loads. The technical features of a larger caliber gun entail a number of consequences, such as the need for more durable structural parts of the entire tank, a more powerful engine, etc. Ultimately, all this affects the price of the finished tank.
The second controversial point of the 140-mm tank gun concept concerns its tactical features. On the one hand, such weapons have significantly higher armor penetration characteristics in comparison with the usual 120- and 125-mm cannons. At the same time, it will not be possible to fit a bulky ammo rack with 140 mm rounds into the dimensions of a modern tank. This will lead to a reduction in ammunition and the corresponding tactical consequences. The confrontation between the power of the gun and the number of shots carried is the topic of a separate controversy.
In general, 140 mm tank guns, like many other types of weapons, have pros and cons. In the current environment, when the development of tanks is not as intensive as in previous decades, the use of new calibers looks like an unreasonable measure. It seems that the military of the leading countries will prefer to remain with sufficient and mastered calibers of 120 and 125 millimeters, and more serious systems will remain a sign of self-propelled artillery installations.
