The trunks of small tools

The trunk is the main part of small arms. The barrel rifled firearms intended for message pool rotational and translational motion with a certain initial velocity in a particular direction by the energy of the powder charge. Rotational movement of the pool, it provides gyroscopic stability in flight attached to it stable flying forward head portion and will not tip over under the influence of air resistance. The combination of the barrel and cartridge determines the quality of ballistic weapons.

The device is due to the appointment of the trunk and arms features of its operation. The trunk as part of the weapon works in special circumstances. In order to withstand the high pressure propellant gases at high temperature, the friction bullet as it moves into the bore and high load service, the barrel must have sufficient strength, provided that its wall thickness and material and capable of withstanding the high powder gas pressure 250 — 400 MPa ( to 4000 kg / cm ²) at a temperature reaching 3000 ° C. During the combat use of weapons trunk is exposed to different loads (with bayonet charges as a bayonet attached, usually directly to the trunk, with military use of weapons, including at shots from a grenade launcher, as it falls, and so on). Outer shape of the trunk and the thickness of its walls are determined by the strength, cooling, mounting method barrel to the receiver, mounted on the barrel sights, flame arresters, muzzle brakes, and parts designed to protect against burns, handle, barrel lining, etc.

On the trunk distinguish the breech, and the average of the muzzle. Muzzle (front) of the barrel muzzle ends. Muzzle end of the barrel — a cross-section through the front end of the barrel without a flame arrester (compensator muzzle brake). Form muzzle rifling excludes accidental damage, worsening marksmanship. The rear of the trunk is called the breech, and the rear end of it — stump trunk.

Inside the barrel has a bore in which there are: chamber serving to place the cartridge; Puligny entrance, which transition portion of the barrel from the chamber to the threaded portion, and a threaded portion. The barrels of various types of weapons on the device of about the same and differ only in the outlines of the chamber, the caliber and the number of grooves. The chamber shape and size corresponds to the sleeve, and its structure is determined by way of fixing it to the sleeve. The chamber should provide free entry cartridge good fixing sleeve and obturation of the powder gases, as well as ample free extraction cartridges after the shot. On the other hand, the gap between the sleeve and the walls of the chamber must be minimized because too large fordivisor can lead to rupture of the liner.

To ensure tight fit liner appropriately selected longitudinal dimension of the chamber, the values of these dimensions are determined by way of fixing sleeve (on the rim at the front slope), which in turn depends on the design of the latter.

The trunks of small arms

Walther pistol R.38 incision in the chamber a barrel cartridge fixed front cut sleeve

If the sleeve has a protruding lip (flange), the emphasis is usually fix this lip in the trunk stump. With this method of fixation allowed large errors in the longitudinal dimensions of the chamber and the barrel itself. However, these sleeves are usually complicate feeders rounds and is now rarely used, although it was under domestic 7.62mm rifle cartridge having a sleeve with a prominent rim, designed all the heavy machine guns and uniform: SGM, PC / PCM, PCB, PCT, and the SVD sniper rifle.

If the sleeve is not a projecting rim (flangeless), the fixation is usually a ramp to ramp the chamber liner. In this case there is a need for a sufficiently precise manufacturing ramp chamber, causing the chambers to improve the accuracy of manufacturing and cases. Examples of this can serve as a wafer 7.62 mm submachine gun cartridge mod. 1943 and 5.45-mm cartridge 7N6 used in vending machines, and light machine guns Kalashnikov.

For pistol cartridges fixing sleeves are most often cut Dulcitol front liners. This fixation provides the most simple device chamber in the presence of the sleeve without serving chimes, but for other kinds of ammo is unreliable. Therefore, it applies only to a pistol cartridge, having a cylindrical sleeve, for example, a 9-mm pistol cartridge to the gun PM.

In most kinds of automatic weapons beginning extraction (extraction) liner comes at a time when the pressure of powder gases in the trunk still remains quite large. Good obturation propellant gas is close fit to the walls of the walls of the sleeve chamber for a sufficiently long. For this purpose, when the sleeve is moved back at high pressure propellant gases (with free systems and blowback), sometimes in the rear chamber as a cylinder surface which eliminates breakthrough propellant gases even at large offsets it back. Such a surface largely reduces jamming of the conical sleeve in the chamber after firing and after decay longitudinal deformations of locking because the greatest wedging portions are typically the bottom of the sleeve. In some types of weapons of frictional forces between the sleeve and the chamber may be so large that when removing the liner may occur its transverse rupture or damage to the rim ejector. To reduce these frictional forces are sometimes applied in the chamber Revelli grooves which create pressure on the certain part of the outer surface of the liner, facilitate its extraction (extraction). Due to the complexity of manufacturing, rapid contamination and difficulty in cleaning the grooves Revelli in modern weapons are rarely used.

Puligny input connects the chamber with the threaded portion of the barrel and is used to place the bullet head with a view to ensuring its smooth cutting into the rifling of the barrel. In rifles Puligny input consists of a 2-cones, the first of which reduces the diameter of the chamber to the diameter of the rifling fields. The second cone is used to provide a gradual ramping bullet in the rifling (in shotguns This cone is missing). From the size and shape of Puligny entry depends close grouping of weapons. Flight stage length input ranges from 1 to 3 calibers.

Caliber — a unit of measurement adopted in arms to measure the inside diameter of the bore and the outside diameter of the bullet. Caliber rifled barrel is defined as the distance between two opposite or fields Barrel, or — between two opposing rifling. In Russia, the caliber of the barrel is measured by the distance between two fields. In this case, the caliber of bullets in relation to weapons than the caliber of the barrel to provide a bullet in the rifling plunge to purchase a bullet rotary motion. Thus, the diameter of the trunk Makarov PM by rifling fields is 9 mm and the diameter of the bullet is 9.2 mm. Caliber gun barrel is indicated in the system of measures adopted in the country of origin weapons. In countries where the metric system is used to refer to millimeters, and in countries with inch system of measures — in fractions of an inch. In the United States the caliber specified in hundredths of, and in the UK — in thousandths. With all of this caliber written as an integer with a dot in front, for example, the American gun Colt M 1911 A1 .45.

In various armies adopted different forms of rifling. In the Soviet Union / Russia adopted a rectangular cross-sectional shape of grooves, with all the depth of grooves is 1.5 — 2% of the caliber. The remaining sections of grooves used in a v
ariety of foreign samples, for example, trapezoidal profile — Austrian 8mm magazine rifle Mannlicher M 95; segment profile — in Japanese 6.5-mm magazine rifle Arisaka Type 38; oval profile — by Lancaster, beveled profile — in French 7.5-mm machine guns Chatellerault M in 1924.

The direction of the rifling in the barrel may be right (in domestic samples) and left (England, France). Any advantages of rifling different direction does not matter. Depending on the direction of grooves only change the direction of derivation (lateral deviation) of the rotating bullet. In the domestic small arms adopted rifling right direction — from left to right as the upward movement of the barrel bore from the breech to muzzle his part. The angle given to rifling provides rotary motion bullet for all that its stability in flight depends on the speed of a bullet. The stroke length of grooves (lengthon barrel, which rifling make a complete revolution) also has a significant impact on accuracy. Step rifling AKM is 240 mm gun DShKM — 381 mm KPV machine gun — 420 mm.

The length of the barrel rifled arms of each sample is selected from the condition of obtaining the required muzzle velocity. Application of the same cartridge in the samples with varying weapon barrel length allows for different muzzle velocity (see Table)..

The trunks of small arms

The table shows that the range of direct youboom increases with the initial rate for the same cartridge, which affects the improvement of flat trajectory and increasing the destructive space. With increasing initial speed increases the efficiency of the bullet on target due to the greater energy of the bullet. For example, at a distance of 1000 m bullet taken off from the trunk of a PC machine gun, has the energy of 43 kg / m, and the bullet taken off the barrel machine gun — 46 kg / m

In the shot-gun hunting guide portion of the barrel is smooth (without grooves), and it may be part of the muzzle is tapered (conical or parabolic) or extended. Narrowing of the canal called chokom. Depending on the size of the restriction, which improves shooting accuracy, distinguish poluchok, middle choke, choke, choke strong. Expansion into muzzle called flare increases dissipation fractions and can be designed as a cone or another shape.

Trunks in small arms constructively differ on trunks — one-piece bonded and trunks. The trunks are made from solid metal billets, called trunks-piece. However, to increase the strength of the barrel is manufactured from 2-yi or more pipes, equipped on one another with an interference fit. This trunk is called stapled. Bond trunks is not widely used in automatic weapons because of the complexity of manufacturing. Connect the barrel to the receiver with interference can be regarded as a partial bond.

Efficient cooling of the barrel for a modern automatic weapons is of utmost importance. The leading portion of the bullet, in the rifling bumping gave substantial plastic deformation and have thus an additional pressure on the walls of the bore. Barrel wear caused by friction on the surface of the shell bullet moving to large friction force at high speed. Going straight for the bullet, and partially breaking into the gaps between the walls of the barrel and the bullet, the gases produce an intense heat, chemical and erosive effect on the barrel, causing it to wear. Fast abrasion of the barrel leads to a loss of some essential for effective fire parameters (scattering increases bullets and projectiles becomes unstable in flight decreases below a predetermined initial limit speed).

When strong heating barrel decrease its mechanical properties, resistance decreases barrel walls action shots, it leads to increased wear and reduced viability of the metal stem. When strongly heated barrel due to the emergence updraft difficult aiming. Heat breech may result that the cartridge, having sent the chamber after termination of fire may reach autoignition making gun handling unsafe. In addition, the large bore makes it difficult to heat up arms. To the arrow is not affected by the burns on the arms are mounted special plates, handles, etc.

Heat the powder gases caused by rapid heating of the barrel automatic weapon during firing. It follows that the intensity of the heating power depends on the barrel for each shot and fire mode. For weapons designed to fire a single low-powered ammunition (pistols), cooling the barrel is of secondary importance. For the weapon, firing powerful ammunition (machine guns), cooling must be more effective than more capacity magazine (tape), and the more long-term continuous shooting must be conducted in a given sample of weapons. Image barrel temperature is above a certain limit reduces its strength and durability characteristics. All of this ultimately limits the rate of fire (ie, the allowed number of shots during continuous shooting).

The special ways of cooling trunks include quick-change barrel cooling the heated barrel, an increase in the surface of the cooling bore through the ribs, the application for the same purpose of various kinds of nozzles (radiators), artificial blowing outside or the inside surface of the barrel, the application of liquid chillers, etc. Currently, the most widely used two types of cooling trunks — air and water.

The trunks of small arms

The cut Colt 1911A1 M, where a parting at dismantling the barrel is attached to the frame by means of earrings

Air cooling has become commonplace among modern types of weapons due to its simplicity, but it does not provide a high rate of heat transfer to the air.

To improve heat transfer trunk typically increase its surface with special transverse or longitudinal edges. The effectiveness of this method is determined by the number of fins and the trunk. The use of ribs on the outer surface of the barrel while increasing the overall heat transfer area with air, but it leads to uneven heating of the metal stem and ultimately reduces its total specific heat. However, increasing the hole edges leads to its weighting, which is disadvantageous. Have been attempts to use worn on the edges of the trunk, made of light alloys. However, this method has spread because of the difficulty of making such trunks. To improve heat transfer devices have been designed that improved air circulation and blowing barrel by blowing its outer surface. For example, in the English manual machine gun Lewis M 1914 on the barrel placed over the radiator to the longitudinal edges of the alloy and on the radiator shroud was put on a tube. During the firing opening of the barrel forms a propellant gas stream in front of the vacuum casing, whereby the air sucked into the casing and extends between the rear edges of, increasing the intensity of cooling. The use of this structure increased the intensity of cooling the barrel during firing, but with all this, it was found that in the intervals between bursts cover prevented the flow of fresh air, which ultimately did not improve the cooling of the barrel.

At present, modern designs of automatic weapons, air-cooled barrel (heavy machine guns) is often ribs on the trunk does not have either make them very small, using thick enough trunks, for example, in the Austrian 5.56 mm assault rifle AUG on the trunk just nakatana screw-thread with a pitch of about 1 mm. For light weapons (
rifles and light machine guns) or limited rate of fire, or (for the light and heavy machine guns) are used quick-change barrels, allowing in a combat situation quickly replace the heated barrel and these provide a high fire mode. With all of this stems automatic weapons have, as a rule, large reserves of strength. The thicker barrel, having a large heat capacity, less heat from shot to shot, which increases the duration of continuous fire until the dangerous overheating of the trunk and increases its service life. In this regard, the trunks under the same cartridge in the weapon, intended for use in hard mode of fire (eg, common guns PC / PCM), have a thicker barrel than the weapon, which has a relatively low practical rate (SVD).

Especially effective is a water-cooled barrel, has received in the past widely used in heavy machine-guns. Its special feature is the sharp drop in temperature in the trunk of minor breaks in shooting due to intense heat transfer from the trunk to the cooling fluid. To cool a normal-caliber machine gun barrel is enough to have a supply of water in the casing of the order of 3-4 liters, and for large-caliber machine-gun 5-8 liters. Such a cooling system allows continuous fire before the time, until all the water boils away. However, the presence of the casing with water greatly complicates the design of weapons and its operation, as well as increases the vulnerability of the weapons in combat. An example is a domestic 7.62mm machine gun Maxim arr. 1910 In addition, water-cooled barrel has a number of disadvantages: requires a constant supply of water at a low temperature water freezes, it can damage the casing and the barrel; increases the mass of weapons to the detriment of maneuverability, the complexity of the preparation of weapons to fire, high vulnerability weapons in combat, etc.

Because of these deficiencies in the water-cooled barrel modern weapons are not applied, but has been successfully used in fixed-type automatic weapons, such as ship installations.

There are two main types of stem attachment to the receiver: plug-in connection to the receiver barrel weapons, providing a quick change barrel without disassembly of weapons, and the one-piece, is not provided.

Most current models of small arms, the life which is the same as that of the trunk (SVD sniper rifle, submachine AKM/AK-74, machine guns RPD / RPK / RPK-74 and a Makarov pistol) without having the device for a quick change barrel, the trunk is connected to the receiver permanent connection. This may be screwed to interference, such as in semi-automatic rifle Dragunova or cylindrical coupling surface with the additional fastening pin. The barrel assembly to the receiver in this case is carried out in the factory.

Attaching at dismantling separating stems can be made by a bayonet, screw, stud or earring. The last two types are used in some pistols, providing ease of disassembly and cleaning. An example is the mounting hole Tokarev TT pistol. In addition, the plug-in connections trunks with a receiver (not providing a quick change barrel) are commonly used in heavy machine, uniform and heavy-caliber machine guns PC CPV DShKM, NSW and their modifications. Plug-in connectors allow in-service weapons to replace the heated barrels of spare and thereby provide an opportunity to conduct an intensive and long-lasting fire (as long as the barrel is made from a single shooting, the other cools.) In addition, the presence of a removable barrel increases the survivability of weapons.

The trunks of small arms

Spare barrel with a single machine gun holster MG.42

Quick-change barrel plug connections to the receiver are usually carried out rusk or wedge. These compounds are mainly used for light and heavy machine guns. Soekarno-threaded connections do often screw, for example, in the 12.7-mm DShK arr. 1938 Sometimes when you connect the barrel turns, and sometimes special coupling. In some cases, the barrel just invested their rusks projections into the corresponding slots receiver. In systems with a moving barrel for attaching trunks to the receiver sometimes use special tabs on the trunk (the spikes in the Maxim machine gun mod. 1910) In addition, a removable trunk is connected to the receiver and also the wedge connection. Thus, the machine gun barrel DShKM connection to the receiver is a wedge. Despite the simplicity of the design, such a compound is inconvenient to use, because to replace the barrel, unscrew the nut and knock out the wedge. An improved design of this type is used in heavy machine gun NSV. In systems with a fixed barrel — machine guns PC / PCM, SGM and their modifications — used wedge adjustable to compensate for wear lugs bolt. By adjusting the distance between the bottom of the cup gate and cut a treasury trunk (mirror gap) provided close the bolt and eliminates the appearance of a delay in the form of cross-break barrel during firing. In order to facilitate the separation of the barrel from the receiver when heated outer surface of the breech PKM / PKT chromed.

At the muzzle of the barrel can be attached devices for various purposes. So, on the trunk of AKM 1959 — 1962 model years clutch is installed to protect the thread from damage, and on the trunk of AKM 1963 — 1975 years of manufacturing fixed compensator to improve the accuracy of the battle by firing bursts on the move, standing and kneeling. The compensator has a threaded portion which serves to connect with the muzzle of the barrel. Front end of the compensator is designed as a projection with an oblique cut. Inside the projection made groove forming the compensation chamber. Powder gases after leaving the barrel is pressurized, which rejects the muzzle towards the ridge (left down). In the AK-74 used two-chamber muzzle brake compensator, at the same time fulfilling the role of a flame arrester, which greatly enhanced the stability of the weapon during firing. On trunks RPK, PK / PKM, SVD sniper rifle and AKM, with a night sight mount, mounted slotted flame arresters are designed to reduce the emission intensity heated to a high temperature powder gases and particles of gunpowder Dying at the exit of the barrel. Reduced visibility muzzle flash is achieved by the majority of its closed side walls flame arrester. PKT machine guns, SGM, KPVT, NSW have fire extinguishers with a tapered socket. This flame arrester due to the inflow of air into it provides intensive after-burning of the powder particles and decreases the brightness of the muzzle flash when shooting.

Flame arrestor KPVT has a more complex structure consisting of a proper flame arrester base muzzle, the barrel bushing and piston. In connection with this flame arrestor KPVT except dimming muzzle flash provides increased energy rollback rolling barrel.

On trunks can also be installed muzzle brake designed to reduce recoil energy of the barrel due to removal of the powder gases in the lateral directions and to reduce its expiration in the axial direction.

On trunks of arms, working on the principle of using the energy of the powder gases discharged through the hole in the side wall of the trunk, mounted vent device. These devices have a narrow inlet portion associated with the bore and an outlet portion broadened — gas chamber. In the gas chambers trunks PC / PKT, SGM, RPD, SVD gas regulators are set to ensure reliable operation of automation in various operating conditions. This is achieved by changing the toamount of powder gases acting on the piston bolt.

The following methods for controlling the intensity of the action on the gas piston bolt:

  • Changes in the
    area of minimum cross-section of the gas pipeline through which the outflow of gases from the barrel into the gas chamber machine guns (FCT, SGMT). Such a construction of the gas regulator can reduce the fumes inside the tank combat vehicle;
  • discharge of gas from the chamber to the atmosphere (SVD rifle, machine gun PC / PCM). Maximum rate of bolt holes is closed, because in this case the maximum amount of gas will be supplied to the piston bolt.

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