Mortar

American mortar crew in action near the Rhine, 1945

American mortar crew in action near the Rhine, 1945

The mortar is a piece of artillery fire arc (the angle of the rod is always greater than 45°) used for indirect fire support by launching projectiles at low speed and beat for goals that cannot be affected by the pull of artillery in direct fire, as places behind vertical obstacles. Typically, the length of the barrel is less than 15 times the caliber, but there are exceptions.

Normally, the mortar is the weapon used for its support of fire from infantry units.

It is simple to implement, being constituted essentially by a rod and by a support plate, and also is simple to use and allows a remarkable rate of fire, the projectile being normally loaded directly from the mouth of the weapon.

History and Evolution

The origins

The first firearms were developed in Europe with the discovery of gunpowder, were not portable: the methods of construction were handmade and included a wooden base on which to secure the barrel. This was essentially a “tube” obtained by fusion of bronze or by a series of “strips” of wrought iron juxtaposed side by side according to their length and kept together by circles (also iron) external pressed on the bars along the inner circumference of the circles themselves.

The rods thus obtained were open at both ends, but having to be open only one to constitute the “mouth” from which would come out the projectile, the rear end was closed in various ways, sometimes simply with the wood-based (in this case suitably shaped) that blocked this opening, other times by fixing a lid-shaped metal barrel, or still supporting the barrel (this time in the form of “beer” with a “handle”) that remained in place thanks to form the basis of wood, leaving him free to be removed with a vertical movement, in order to be from time to time “loaded” by inserting the charge of black powder and the projectile. In the latter case, the weapon was muzzle-loading, but breech and could be available to more “barrels” previously loaded for a repeat stroke faster.

At this time (we are at the dawn of firearms: XIV century) wars were still fought with sides of men with weapons (spears, swords, halberds, maces, etc..), So the first weapons systems using powder shot were mostly used during sieges to castles and fortresses: This soon led to development of “guns” from the pull very curved, most likely to hit the top of the opposing walls (bombards) or to throw projectiles over the wall itself (the mortars), leaving to the various types of cannons by shooting tighter (called falconets, culverins, cannons and basilisks, according to the increasing size of the projectile launched) the task of demolishing the lower parts of the walls.

To get a shot much more curved, the artisans of the time (early fifteenth century) realized that it was necessary to launch a projectile at low speed with a wide-angle upward once reached the apex of its trajectory, the projectile would fall almost vertically on opponents.

The method for obtaining this result was to build firearms with a reed very short (1.5 or 2 times the caliber of the bullet) already fixed to its base with the mouth facing upwards: not perfectly vertical to avoid shot the ball came back to hit the piece and its crew, but with great inclination to get the shot vertically towards the enemy.

A reed so short could be built using a single casting of bronze and the result had the appearance reminiscent of a mortar, the tool in the shape of the container, which is still used to grind and pulverize various materials through the use of a pestle (both in the kitchen in the pharmaceutical field).

Both the mortar bombs were shooting up the characteristics of curved and often mingled with those of the other, so as to become almost synonymous in certain historical periods.

With the barrel attached to the wooden base, to vary the range of the shot needed to adjust the amount of powder propelling charge or vary the distance from the target approaching or moving away from it, but at the beginning of the sixteenth century began to appear the first systems elevation. Setting the basis of the barrel with a pin could vary the elevation putting a wooden block in support of the barrel itself: more approached the wedge toward the rear of the barrel, the latter is more inclined raising its mouth: in this so it was possible to vary the range of the projectile with a given firing charge.

Appeared also the wheels applied to the wood bases of support and thus the first carriages for towing by animals.

In the nineteenth century

Except for the construction methods that improved machining tolerances, reducing the “wind” (distance between the inner walls of the barrel and the outer surface of the projectile, from which flowed part of the gases created during the explosion due ignition of the powder, with consequent loss of gas and speed on the part of the projectile, as well as having poor precision for the high flow disturbances of the gas itself) and making possible a standardization of parts and of projectiles (starting from the first of the eighteenth century), the structure of mortars remained almost unchanged until the first half of 1800, when, thanks to the ‘industrialization, there was a first big change.

From those years was the creation of the barrels for “solid drilling” means drilling.

Also came into use bullet-pointed cylinder or cylindrical-conical in need of some stabilization system of its flight was in 1853 that began to appear the first rifled mortars, with use of the same in siege operations during the War of Crimea (1854 – 1856) along with mortars large.

The wall thickness increased in thickness to increase the propelling charge and allow the launching of projectiles larger (and more weight) always loaded from the mouth.

During the American Civil War (1861 – 1865) were used mortars and siege of the fortress cities, while in the Franco-Prussian War of 1870, the Prussians utilized heavy mortars rifled.

It was during the First World War who was born the ancestor of infantry mortars of the twentieth century.

In 1915 fact Sir Wilfred Stokes launched the prototype of its mortar, consisting of a cane much shorter and lighter than the mortars siege generally in use.

This rod rested directly on the ground via the interposition of a rectangular metal plate which increased the area of the land on which discharged the force of recoil upon firing. In addition, there were two metal arms that supported before the barrel to which they were attached by a metal collar.

The most important innovation, however, was the use of a cylindrical shell with a pointed tip, the end of which was inserted a cartridge rifle with the bottom facing down, while in the barrel, on the bottom, there was a striker fixed: entering the projectile with the sleeve at the top of the mouth of the barrel, this fell along the soul of the same by gravity and traveled its length, the capsule booster present in the cartridge hitting the firing pin fixed to the bottom of the barrel, triggering the firing charge in the shell which was enough to start the bomb.

At that time, the Germans developed a weapon called “minenwerfer” (literally “pitcher of mine”), which replicated the shape of the mortars of the time but with decidedly smaller dimensions. It was produced in three versions: with sizes ranging from 25 cm, 17 cm and 7.58 cm, and they were all three rifled firing a projectile with a band preincisa with loading from the mouth.

The model to be 7.58 cm, in particular, firing a projectile which also contained the firing charge in its rear part as in the case of mortar Stokes, even if the barrel extremely short did not permit the projectile to fall on the firing pin with sufficient force to trigger the firing charge, for which the weapon was equipped with a simple manual firing pin movable on command to perform this task.

In any event, the First World War saw the use of the usual mortars both large and large-caliber artillery used in accordance with the typical procedures, both the use of mortars smaller and lighter distributed directly to the infantry and from these managed for their fire support.

The latter use was the one that most pushed the development of these weapons. The large mortars of 800 were proving increasingly incapable of evolution that were having the methodologies of conduct on the battlefield, while the use of light mortars used directly by the infantry as light artillery to employ, married perfectly with the use of new tactics that were being developed.

The appearance of the tank on the battlefield was giving birth to new doctrines (such as those that would have been developed in the postwar period by Fuller or Guderian), which included not only the massive use of armored vehicles, but also the use of forces in maneuvers deep and fast. It was evident that the infantry would have to move quickly, and just as quickly use to support their own weapons supplied: the mortar derived from that developed by Stokes was perfect, could be distributed directly to the infantry units they could rely on it as was a small portable artillery ready and exclusive use, without having to ask and wait for a fire support provided by other units (artillery), which often was not timely nor (had to be requested by climbing the various chains of command) or adhering to the prevailing .

With the Second World War saw the use of mortar attacks by all the belligerent armies according to the methods that are still in use today and mortar infantry had taken its final shape.

The mortar modern categories and types

The modern mortar is directly derived from the models seen on the battlefield during World War II. It then became the typical piece of artillery supplied direct to infantry units, including the minor ones, representing “the artillery staff” that are available to the commander of a battalion or company.

Depending on the level of the department in which it is distributed, the mortar must meet different requirements in terms of lightness, portability (also by the decomposition of the piece in more loads) and radius (the larger, high-level department, the more require a longer range to support the lower units). In general, the mortar distributed at the team level / infantry platoon, is a mortar superlight of caliber normally between 45 mm and 60 mm, consisting simply of the barrel in its rear section is fixed bearing plate reduced: the weight is content than allowing the transport by one man and this type of mortar is called “commando”.

Always to keep the weights within certain limits, also the mortars distributed at the level of company (if this is light infantry) have a caliber of 60 mm (as the model M224 U.S. Army) and are called light mortars. The mortars are the average of 81 mm (82 mm for countries linked to the former Soviet Union) that are distributed at the company (in the case of mechanized infantry) or battalion level (in the case of light infantry). Instead, they are 120 mm (or 107 mm for the armies that still use the mortar previously supplied to the U.S.) the heavy mortars distributed to battalion level (in the case of mechanized) or regiment (both mechanized infantry that light).

With the advent of mechanization of the majority of infantry, even the heaviest mortar could be widely distributed at levels low enough orders: being installed on vehicles tracked or wheeled, so failing the concern to build the pieces in order to be broken down into individual loads with weights and dimensions certainly shoulder-carried by infantry, it has become more convenient to have fairly high caliber mortars.

In addition, the mechanization provided input for theories of employment of mortars that are similar to those applied for the use of artillery support to large units, for which they were developed both automatic mortars with high rates of fire, and mortars of caliber well above average, everyone installed on armored hulls.

Very active in this field was Russia, which has developed several systems on the basis of lessons learned during World War II fighting against Germany, who first sided giant mortars placed on moving platforms Crawler (six mortars, 610 mm Series Gerät 040 built and designed by Karl Mörser and called Adam, Eve, Thor, Odin, Loki and Ziu) and infantry mortars of 81 mm halftrack Sdkfz 250/7.

In the sixties the Soviets fielded the mortar on the hull tracked 240 mm 2S4 Tyulpan (M1975) breech which fired a projectile at 12 km away with a rate of fire of one or two shots per minute (a rate lower than mortars smaller, however, concerned that blows from 130 kg each). Subsequently entered service a mortar high rate of fire (4 shots in two seconds) from 82 mm placed in the turret of armored tracked MT-LB: the 2B9 Vasilyek.

Like Russia, the countries of the western North Atlantic Treaty Organization have developed automated systems to increase the rate of fire of mortars, but so far, most of them have not been adopted, remaining such systems “technology demonstrators” capabilities of the various war industries who trained in these developments.

By contrast, the NATO member states have developed many models of mortars lightweight and compact for use at levels lower orders (infantry squad and platoon) and by special forces acting groups using numerically reduced.

They also emphasized the development of mortar shells advanced technology to maximize the effectiveness of individual shots: shots have been developed “cluster” with sub-munitions specialist depending on target to beat, blows against tank with autoguiding like English ” Merlin “81 mm or Swedish Saab-Bofors Strix 120 mm self-propelled and strokes to improve the range.

Light mortars and “Commando

The mortar is a light infantry mortar of size and weight that can be carried by a single man and used by infantry units of the lower level (squad and platoon).

Given the dimensional limitations, the caliber of such weapons is never greater than 60 mm and consequently the maximum range is reduced: the mortar light with the greatest range is the American model M224 (which has replaced the previous M19), which can reach 3490 meters when used in a conventional manner with bipod, increased support plate and pointing system, but in this case assumes characteristics in terms of weight (over 25 kg) which put it at the limit of the category of mortars medium and which require it can easily be broken down into three modules (base, barrel, bipod), one per person, to be able to easily carry on their shoulders. This mortar can also be used in lighter version (only the barrel and a support base reduced) and in this case can be carried by a single jack (in this configuration, the M224 does not reach the 10 kg).

The M224 model is still the limit of the category: the true representatives of the mortar are lightweight models M2 and M19 Americans, both produced since the Second World War, always with smooth bore in 60 mm caliber and spread all over the world. Very light (about 13 kg), with base plate and bipod, very short barrel (which allowed for a useful range of about 1000 meters), have been used in combat by the U.S. in 1942 and participated in the Korean War and the Vietnam War. Adopted by the majority of Western armies belonging to NATO, are also present in many countries on all continents, both in the regular army in irregular units.

Similar was also the mortar Hotchkiss-Brandt (always 60 mm and also smooth bore) supplied to the French (it is employed in the war in Indochina that the Algeria) and which was taken as a model for same M2 and M19 Americans and remained in service until the end of the nineties, while the German mortar Granatwerfer Model 1936 50 mm of World War II had a larger base of support that went before sufficiently to eliminate the need for bipod (which in fact was not present nor expected). Other lightweight mortar was Brixia 45 mm Italy no.

Since the Second World War, this type of mortar was distributed to infantry platoon or company level, with the progressive trend (since the sixties) to deploy this kind of light mortars at the top (removing them from the platoon level) and then, with the progress of mechanization department, to replace them with mortars of greater caliber and weight. Proceeding in this place, came the need for support of fire shot curved for smaller units: this led to the development of launchers hooked directly to the assault rifle that comes with the jack, and the development of type mortar “commando”.

The mortar commando is nothing but a lightweight mortar private bipod and equipped with a support base extremely reduced, often without additional sighting devices: the resulting weapon is very light and portable with ease even by individual soldiers framed in very small units: an example is the Austrian mortar Hirtenberger M6C 210 60 mm adopted at the beginning of the XXI century as well as departments’ Italian Army.

The emergence of this type of mortar dating back to the First World War, in particular to some types of grenades that were used on the Italian-Austrian front on both sides: hand made almost disappeared at the end of the war.

The first mortars with the typical characteristics of the type “command” appeared during World War II and were the British from 2 inches (51 mm) and Japan is 50 mm: both supplied to the respective armed forces were deployed to the level of team. The British, in particular, will continue to maintain the supplied an improved version (the mod. L1) distributed to platoon level.

The time now is weapons supplied mainly to the Special Forces for their specific needs in the field of their own indirect fire support.

Average infantry mortars

This is the type that best represents the mortar infantry itself.

It is distributed at the company or battalion and its shape is now crystallized on the model of Hotchkiss-Brandt mortar which in turn comes from what Stokes realized in 1915: base plate to which it is joined by the barrel (normally smooth-bore) supported by a bipod.

Can be decomposed into three loads, allowing the transport to shoulder by three men.

The caliber of these weapons has now stabilized on the 81 mm to those supplied to the armies on the Western and 82 mm for those built in the former Warsaw Pact countries bound: therefore the power of the blow and the rate of fire is high enough provide support to fire effectively, the range is necessary to enable targets to beat in the interest of a unit at company / battalion (from 3000 to 6000 meters, depending on the model adopted and ammunition) but remains dimensions and weights “manageable” even by light infantry units.

Heavy mortars

The heavy mortar is currently the element that provides the largest fire support self framed in infantry units.

While the development of medium and light mortars took place mostly in Britain and France (with the other nations copied, improved or produced under license what these forces mettavano in service, and as mutuavano the doctrine of employment) mortars Soviet heavy were an invention of the 30s, which replaced the big bombs of World War weapons handy and reliable. Caused a shock in the first few months of operation Barbarossa, during the Second World War, and especially during the battle at the gates of Moscow, the Germans and Italians that they ordered similar models (the German one, in practice, a certified copy was the only to enter service) and hastily put into service all the specimens that failed to capture.

Size is generally 120 mm in both the armies of NATO countries and in the countries belonging to the former Soviet bloc (Warsaw Pact): even the United States of America that previously used the rifled mortar M30 107 mm (4, 2 inches) have adopted the model M120 smooth bore 120 mm conforming to what is used in other countries.

While there are larger caliber mortars, such as 240 mm used by the Soviets and 160 mm is used by Russians to Israelis, these are used mainly as artillery pieces themselves, framed in self-contained units for a particular purpose.

The morphology of the heavy mortar is similar to that of mortar medium by infantry, even if the larger size and the greater weight, in addition to the complete mechanization of modern armies, has led to the development mortars that tend to differ from the typical mortar by infantry, replacing the bipod with trolleys rotated which allow the mechanical coupling of the mortar already composed (as is the case of the Thomson Brandt MO-120-RT-61) or by replacing the bearing plate directly with the floor of the vehicle (especially if armored) which carries it and employs: mechanized units using armored vehicles in fact derived from the troop transport vehicles specially modified for use aboard the heavy mortar (as is the case of the vehicle portamortaio M106 M113 derived from VTT).

Mortars details

Can be cataloged mortars particular those which, for practices or by type, varies from what is described for the various types of mortars terrestrial infantry.

In the area of land is worth mentioning the large-caliber mortars (160 mm or 240 mm) and for their reduced diffusion (they are used only in the countries of the former Warsaw Pact, Israel and the Scandinavian countries) and for the type of ‘use (using heavy bullets, require logistical support that precludes its use when framed in the base units of infantry, so these pieces are framed in self-contained units with usage patterns very similar to those of conventional artillery) that for the fact that they are also designed for the use of tactical nuclear munitions (at least in the case of mortars of Soviet origin).

In the marine sector have been used different weapons based on the concept of anti-submarine mortar, especially during the Second World War are an example of the Hedgehog Anglo-American, the next Squid and Limbo, as well as systems Bofors after the war.

Morphology of typical mortar infantry

The typical infantry mortar is directly derived from the model of Wilfred Stokes in 1915.

The weapon consists of four main parts:

•      cane

•      support plate

•      bipod support

•      Pointing device

The barrel is a simple metal tube with one of the two open end (called “mouth” or “sprint”) and the other one is closed (called “breech block”). It performs the typical functions of each tube:

•      provide the environment where it can burn / ignite the propelling charge to fire the projectile

•      provide leadership to direct the projectile shot, forcing him to take the bore along its length in the first stage of acceleration.

At the exit from the muzzle, the stability of the projectile in the ballistic phase of flight, is ensured by the aerodynamic force which is generated on the tail fins present in the shank of the projectile itself in the case of mortars smooth bore, while in the projectiles fired from barreled weapons rifled, the stability is generated from ‘gyroscopic effect imprinted by the helical grooves present in the soul of the barrel: in this case there are no fins on the shank of the projectile which would otherwise destabilize during the distance of its trajectory.

In the end plate (otherwise “slang” with which is called the rear part of the barrel), are present:

•      within, a striker fixed or mobile depending on the models

•      outside, a pin which often is of type “Uniball”, which allows a high speed both in the actions of elevation and tilt both in the actions of composition / decomposition of the piece for the manual transport in multiple loads. If the firing pin is floating inside, the outside is also the mechanism that allows it to act on the same striker.

In a mortar, the recoil generated by the firing of the projectile, is absorbed by the support plate part which rests on the ground, in which, stroke by stroke, tends to sink if place of sinking into the ground.

The plate is made from a metal surface rather thick circular or rectangular. On one of the two faces (the upper one) is a device to which frame the breech block of the barrel (normally this is the receptacle “female” of the pin “Uniball” present on the rear part of the barrel itself), while on the opposite face (the lower one that is resting on the ground) are present grooves or protruding small “plowshares” which provide a greater “grip” on the ground, and consequently a greater stability of the weapon during firing.

The bipod used especially for the stability of the barrel, which otherwise would be supported only on the plate. Furthermore it is essential for movements of elevation and tilt, as the bipod is provided with mechanisms to “continuous screw” to vary in a precise elevation and direction acting on the relevant adjustment knobs.

Always on bipod, is placed also the sighting system (that is removable and is usually transported from “capopezzo”), consisting of a target optical in turn equipped with manual adjustments for corrections purposes of the shot, both in the vertical plane and horizontal.

Types of mortar shells

The mortar shells are of different shape depending mortars are designed to smooth-bore or rifled mortars.

In the case of projectiles intended for mortars smooth bore, their shape resembles that of a fish: the main body is constituted by a tapered cylinder containing the explosive load, the front part is a cone formed by the fuze (time, pressure or proximity), while the rear part is substantially a cylinder (called tang) of diameter much smaller than that of the main body to which is joined posteriorly and presents a series of fins placed in a radial pattern which serve for the stabilization of the projectile in flight.

Between the flaps and the main body, the shank presents normally of holes: in fact the position of ignition is placed in the inside of the shank of the projectile, the outside of which, in the area between the flaps and the main body, if necessary, are Additional charges placed in the shape of “U” or horseshoe, or also in the form of bags “plans” containing the firing charge that are wrapped around the tang itself. Through the holes present in the shank passing the hot gases generated by the detonation of the primer which will illuminate the firing charge same.

In some types of projectiles, there is no space between the fins of stabilization and the main body, whereby the firing charge Additional is shaped to “V” and is placed directly between two contiguous fins, between which holes are present on the shank that serve for the ignition of the charge.

There are also shots that do not involve the use of additional fillers (and not even have the vent holes on the shank) and the only propelling charge used is that this directly within the shank itself: this kind of shots is generally limited the use of shots from training (inert or less) or for use in light mortars (or command) which are sufficient short radii and light projectile.

In the case of mortars rifled, the projectiles used completely miss the shank (as in the case of bullets for the mortar American M30 to 107 mm, in which the shank is replaced by a “screw” containing the trigger that holds the charges additional in the form of “sheets” square) or, though having it, is of small size and lack of stabilizing flaps (as in the case of the ammunition intended for the mortar French Thompson-Brandt MO120 RT61). In many cases, moreover, the ammunition has on the circumference of the main body of the “invitations” coil for the stripes in the barrel (as used on the aforementioned MO120 RT61 French).

Both in the case of ammunition for mortars smooth bore that rifled, the projectiles are equipped with a modern “sealing ring” around the main body. This ring is made from plastic material thermo-expansive that at the moment of the explosion of the firing charge expands due to the sudden increase of temperature, ensuring the tightness of the gas behind the projectile inside the barrel. In this way, although it could easily slip from the mouth that the projectile, by gravity, can descend smoothly in the barrel, the efficiency of the propelling charge is optimum for obtaining the best ballistic performance in terms of range.

The type of ammunition used in mortars (which is smooth bore ribbed) covers different needs and what can be more conventional:

•      high explosive

•      smoke

•      smoke-arsonist

•      illuminating

To these types, there are also special types of ammunition or special: cluster munitions with submunitions, ammunition against tank guided or self-guided at a distance (such as Merlin or Stryx), IR illuminating munitions countermeasures or chaff.

Current developments and future

The development of the mortar are linked to two antithetical requirements developed with the technological evolution of combat units: the first concerns the need to increase the rate of fire significantly, especially for armored and mechanized units, while the second concerns the need to strike with precision and efficiency targets individuals (not only “of area” as normally employed) even if they were particularly “hard” as bunker or individual tanks.

Notes

Pestle on Wikidizionario

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