1.
Kilogram
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The kilogram or kilogramme is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype of the Kilogram. The avoirdupois pound, used in both the imperial and US customary systems, is defined as exactly 0.45359237 kg, making one kilogram approximately equal to 2.2046 avoirdupois pounds. Other traditional units of weight and mass around the world are also defined in terms of the kilogram, the gram, 1/1000 of a kilogram, was provisionally defined in 1795 as the mass of one cubic centimeter of water at the melting point of ice. The final kilogram, manufactured as a prototype in 1799 and from which the IPK was derived in 1875, had an equal to the mass of 1 dm3 of water at its maximum density. The kilogram is the only SI base unit with an SI prefix as part of its name and it is also the only SI unit that is still directly defined by an artifact rather than a fundamental physical property that can be reproduced in different laboratories. Three other base units and 17 derived units in the SI system are defined relative to the kilogram, only 8 other units do not require the kilogram in their definition, temperature, time and frequency, length, and angle. At its 2011 meeting, the CGPM agreed in principle that the kilogram should be redefined in terms of the Planck constant, the decision was originally deferred until 2014, in 2014 it was deferred again until the next meeting. There are currently several different proposals for the redefinition, these are described in the Proposed Future Definitions section below, the International Prototype Kilogram is rarely used or handled. In the decree of 1795, the term gramme thus replaced gravet, the French spelling was adopted in the United Kingdom when the word was used for the first time in English in 1797, with the spelling kilogram being adopted in the United States. In the United Kingdom both spellings are used, with kilogram having become by far the more common, UK law regulating the units to be used when trading by weight or measure does not prevent the use of either spelling. In the 19th century the French word kilo, a shortening of kilogramme, was imported into the English language where it has used to mean both kilogram and kilometer. In 1935 this was adopted by the IEC as the Giorgi system, now known as MKS system. In 1948 the CGPM commissioned the CIPM to make recommendations for a practical system of units of measurement. This led to the launch of SI in 1960 and the subsequent publication of the SI Brochure, the kilogram is a unit of mass, a property which corresponds to the common perception of how heavy an object is. Mass is a property, that is, it is related to the tendency of an object at rest to remain at rest, or if in motion to remain in motion at a constant velocity. Accordingly, for astronauts in microgravity, no effort is required to hold objects off the cabin floor, they are weightless. However, since objects in microgravity still retain their mass and inertia, the ratio of the force of gravity on the two objects, measured by the scale, is equal to the ratio of their masses. On April 7,1795, the gram was decreed in France to be the weight of a volume of pure water equal to the cube of the hundredth part of the metre
2.
Gun barrel
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A gun barrel is a part of firearms and artillery pieces. The hollow interior of the barrel is called the bore, a gun barrel must be able to hold in the expanding gas produced by the propellants to ensure that optimum muzzle velocity is attained by the projectile as it is being pushed out by the expanding gas. Modern small arms barrels are made of known and tested to withstand the pressures involved. Artillery pieces are made by various techniques providing reliably sufficient strength, early firearms were muzzle-loading, with powder, and then shot loaded from the muzzle, capable of only a low rate of fire. During the 19th century effective mechanical locks were invented that sealed a breech-loading weapon against the escape of propellant gases, the early Chinese, the inventors of gunpowder, used bamboo, a naturally tubular stalk, as the first barrels in gunpowder projectile weapons. Early European guns were made of iron, usually with several strengthening bands of the metal wrapped around circular wrought iron rings. The Chinese were the first to master cast-iron cannon barrels, early cannon barrels were very thick for their caliber. Bore evacuator Bore snake Cannon Muzzle Polygonal rifling Rifling Slug barrel Smoothbore
3.
Shell (projectile)
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A shell is a payload-carrying projectile that, as opposed to shot, contains an explosive or other filling, though modern usage sometimes includes large solid projectiles properly termed shot. Solid shot may contain a pyrotechnic compound if a tracer or spotting charge is used, originally, it was called a bombshell, but shell has come to be unambiguous in a military context. Words cognate with grenade are still used for an artillery or mortar projectile in some European languages, shells are usually large-calibre projectiles fired by artillery, combat vehicles, and warships. Shells usually have the shape of a cylinder topped by a nose for good aerodynamic performance, possibly with a tapering base. Solid cannonballs did not need a fuse, but hollow munitions filled with something such as gunpowder to fragment the ball, needed a fuse, percussion fuses with a spherical projectile presented a challenge because there was no way of ensuring that the impact mechanism hit the target. Therefore, shells needed a fuse that was ignited before or during firing. The earliest record of shells being used in combat was by the Republic of Venice at Jadra in 1376, shells with fuses were used at the 1421 siege of St Boniface in Corsica. These were two hollowed hemispheres of stone or bronze held together by an iron hoop, as described in their book, these hollow, gunpowder-packed shells were made of cast iron. At least since the 16th Century grenades made of ceramics or glass were in use in Central Europe, a hoard of several hundred ceramic greandes were discovered during building works in front of a bastion of the Bavarian City of Ingolstadt, Germany dated to the 17th Century. Lots of the grenades obtained their orignal blackpowder loads and igniters, most probably the grenades were intentionally dumped the moat of the bastion before the year 1723. Early powder burning fuses had to be loaded fuse down to be ignited by firing or a portfire put down the barrel to light the fuse, other shells were wrapped in bitumen cloth, which would ignite during the firing and in turn ignite a powder fuse. Nevertheless, shells came into use in the 16th Century. By the 18th Century, it was known that the fuse towards the muzzle could be lit by the flash through the windage between the shell and the barrel, the use of exploding shells from field artillery became relatively commonplace from early in the 19th century. Until the mid 19th century, shells remained as simple exploding spheres that used gunpowder and they were usually made of cast iron, but bronze, lead, brass and even glass shell casings were experimented with. The word bomb encompassed them at the time, as heard in the lyrics of The Star-Spangled Banner, typically, the thickness of the metal body was about a sixth of their diameter and they were about two thirds the weight of solid shot of the same calibre. To ensure that shells were loaded with their fuses towards the muzzle, in 1819, a committee of British artillery officers recognised that they were essential stores and in 1830 Britain standardised sabot thickness as a half inch. The sabot was also intended to reduce jamming during loading, despite the use of exploding shell, the use of smoothbore cannons, firing spherical projectiles of shot, remained the dominant artillery method until the 1850s. By the late 18th century, artillery could use canister shot to defend itself from infantry or cavalry attack and this involved loading a tin or canvas container filled with small iron or lead balls instead of the usual cannonball
4.
Breech-loading weapon
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A breech-loading gun is a firearm in which the cartridge or shell is inserted or loaded into a chamber integral to the rear portion of a barrel. Modern mass production firearms are breech-loading, early firearms, on the other hand, were almost entirely muzzle-loading. In field artillery, breech loading allows the crew to reload the gun without exposing themselves to fire or repositioning the piece. The main challenge for developers of breech-loading firearms was sealing the breech and this was eventually solved for smaller firearms by the development of the self-contained metallic cartridge. For firearms too large to use cartridges, the problem was solved by the development of the interrupted screw, breech-loading swivel guns were invented in the 14th century. The breech-loading swivel gun had a rate of fire, and was especially effective in anti-personnel roles. Breech-loading firearms are known from the 16th century, Henry VIII possessed one, which he apparently used as a hunting gun to shoot birds. More breech-loading firearms were made in the early 18th century, one such gun known to have belonged to Philip V of Spain, and was manufactured circa 1715, probably in Madrid. It came with a ready-to load reusable cartridge, patrick Ferguson, a British Army officer, developed in 1772 the Ferguson rifle, a breech-loading flintlock firearm. Later on into the century there were attempts in Europe at an effective breech-loader. There were concentrated attempts at improved cartridges and methods of ignition, the cartridge was loaded through the breech and fired with a needle. The needle-activated central-fire breech-loading gun would become a feature of firearms thereafter. The corresponding firearm was also developed by Pauly, Pauly made an improved version, which was protected by a patent on 29 September 1812. In 1846 another Paris Frenchman, Benjamin Houllier, patented the first fully metallic cartridge containing powder in a metallic shell, Houllier commercialised his weapons in association with the gunsmiths Blanchard or Charles Robert. In English-speaking countries the Flobert cartridge corresponds to the.22 BB, the first centrefire cartridge was introduced in 1855 by Pottet, with both Berdan and Boxer priming. The Dreyse Zündnadelgewehr or Dreyse needle gun, was a single-shot breech-loading rifle using a rotating bolt to seal the breech and it was so called because of its. 5-inch needle-like firing pin, which passed through a paper cartridge case to impact a percussion cap at the bullet base. It began development in the 1830s under von Dreyse and eventually a version of it was adopted by Prussia in the late 1840s. The paper cartridge and the gun had numerous deficiencies, specifically, however, the rifle was used to great success in the Prussian army in the Austro-Prussian war of 1866
5.
Rifled breech loader
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The spin imparted by the guns rifling gives projectiles directional stability and increased range. Loading from the rear of the gun leaves the crew exposed to enemy fire, allows smaller gun emplacements or turrets. This was both a safety issue and one of gun performance - all the propellant gas was needed to accelerate the projectile along the barrel. The second problem was speed of operation - how to close the breech before firing, two solutions were developed more or less in parallel, the screw breech block and sliding wedge or sliding block. Hence, unlike with a rifle cartridge, the breech mechanism itself somehow needed to provide obturation. Hence if the block circumference was divided into two sets of threads and gaps, the only needed to be rotated ¼ turn to lock it instead of several turns. The tradeoff was that only ½ the blocks circumference was threaded, until the 19th century, only muzzle-loaders were used. In 1837 Martin von Wahrendorff patented a design for a breech-loader with a cylindrical breech plug secured by a horizontal wedge, independently, Giovanni Cavalli first proposed a breech-loader gun in 1832 to the Sardinian Army, and first tested such a gun in 1845. Advances in metallurgy in the industrial era allowed for the construction of rifled breech-loading guns that could fire at a greater muzzle velocity. Production started in 1855 at the Elswick Ordnance Company and the Royal Arsenal at Woolwich, a degree of obturation was achieved via a cup on the face of the block being forced into a recessed ring on the chamber face. Whatever obturation that was achieved relied on manual labour rather than the power of the guns firing, however, the British Army and Navy preferred to revert to muzzle-loaders until larger high-powered breech-loaders with secure obturation systems that were relatively simple to operate were developed. In the meantime the French persevered with trying to develop breechloaders which combined faster loading than muzzle-loaders, high power, safety, the Lahitolle 95 mm cannon of 1875 with an interrupted screw breech met the first three requirements to a great extent and partially solved the obturation problem. Finally the de Bange system introduced in 1877 solved the problem with an asbestos pad impregnated with grease which expanded and sealed the breech on firing. The de Bange system formed the system for all subsequent screw breeches to the present day. Britain adopted the de Bange breech when it returned to breechloaders in the early 1880s after some experiments with the inferior Armstrong cup obturation system. Loading required the 3 operations in reverse and this was hence termed a three motion block and was slow to operate. While working as a designer for Thorsten Nordenfelt in London. This allowed the block to be unscrewed and swung out in two motions - the two motion interrupted screw breech, bofors continued to use this in medium artillery into the 20th century
6.
Recoil
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Recoil is the backward movement of a gun when it is discharged. To apply this counter-recoiling force, modern mounted guns may employ recoil buffering comprising springs and hydraulic recoil mechanisms, early cannons used systems of ropes along with rolling or sliding friction to provide forces to slow the recoiling cannon to a stop. Recoil buffering allows the maximum counter-recoil force to be lowered so that strength limitations of the gun mount are not exceeded, however, the same pressures acting on the base of the projectile are acting on the rear face of the gun chamber, accelerating the gun rearward during firing. This results in the required counter-recoiling force being proportionally lower, modern cannons also employ muzzle brakes very effectively to redirect some of the propellant gasses rearward after projectile exit. This provides a force to the barrel, allowing the buffering system. The same physics affecting recoil in mounted guns and cannons applies to hand-held guns, hands, arms and shoulders have considerable strength and elasticity for this purpose, up to certain practical limits. For this reason, establishing recoil safety standards for small arms remains challenging, a change in momentum of a mass requires a force, according to Newtons first law, known as the law of inertia, inertia simply being another term for mass. That force, applied to a mass, creates an acceleration, according to Newtons second law, the law of momentum -- changing the velocity of the mass changes its momentum. It is important to understand at this point that velocity is not simply speed, velocity is the speed of a mass in a particular direction. In a very technical sense, speed is a scalar, a magnitude, in summation, the total momentum of the system equals zero, surprisingly just as it did before the trigger was pulled. There are two conservation laws at work when a gun is fired, conservation of momentum and conservation of energy, recoil is explained by the law of conservation of momentum, and so it is easier to discuss it separately from energy. The nature of the process is determined by the force of the expanding gases in the barrel upon the gun. It is also determined by the force applied to the gun. The recoil force only acts during the time that the ejecta are still in the barrel of the gun, except for the case of zero-recoil, the counter-recoil force is smaller than the recoil force but lasts for a longer time. Since the recoil force and the force are not matched. In the zero-recoil case, the two forces are matched and the gun will not move when fired. In most cases, a gun is very close to a free-recoil condition, an example of near zero-recoil would be a gun securely clamped to a massive or well-anchored table, or supported from behind by a massive wall. For example, placing the butt of a large caliber gun directly against a wall, the recoil of a firearm, whether large or small, is a result of the law of conservation of momentum
Argentina
Bangladesh
Botswana
Brazil
Chile
Djibouti
Ecuador
El Salvador
Ghana
Greece
Malaysia
Mexico
Nigeria[5]
Biafran armed forces : captured from Nigeria[6]
Pakistan: 50 ordered from Italy in 1975 and delivered between 1975 and 1978 [7]
Peru
Philippines 250 ordered
Saudi Arabia
Spain
Sudan
Thailand
Venezuela
Zambia
Zimbabwe
