The barrel is one of the core parts of the gun, which is usually made of heat-resistant and non-changeable metal tube. When a bullet is fired, the expanding gas from the gunpowder explosion pushes the bullet through the barrel and out of the gun at high speed.
In ancient times, the barrel of a gun was cast. It was thought that casting was the best method, but it was soon found that the barrel was generally too thick and the head was too heavy, which seriously affected the accuracy of the gun when firing. And when the casting process is cooled, it is very easy to produce bubbles, and it is difficult to achieve smooth surface of the barrel bore.
As an important part of the gun, the barrel is also the part with the worst working environment and the highest mechanical performance requirements. It often needs to work in high temperature and high pressure environment. Under these conditions, the structural strength of the barrel is very strict. If the quality is not up to standard, it not only affects the accuracy of shooting, but also may explode the chamber. The quality of a barrel directly affects the service life and performance of the gun, so the processing technology of the barrel has become particularly important. (We recommend you to pay attention to the "mechanical Engineer" public account, the first time to master dry goods knowledge, industry information)
When a gun is fired, the pressure inside the barrel is subjected to hundreds of megapascals, equivalent to thousands of atmospheres. That means thousands of kilograms of pressure per square centimeter inside the barrel. The bore pressure of domestic small-caliber rifle cartridges is about 280-290 mpa, while the bore pressure of NATO small-caliber rifle cartridges is over 350 mpa.
The iron bar used for the barrel is not ordinary iron bar, which is called the barrel blank. Gun casting billet in a steel plant, and then after machine tool cutting into alloy rods can be transported to gun factory, according to the production of the alloy rod type gun gun factory processed into the shape of the design, then start drilling, alloy bar at this time has become "seamless steel pipe", then there is the key technique of gun grooves, finally complete the crossing the paint, a barrel was born.
The materials needed to manufacture high-quality alloy blanks were difficult to obtain. In 1890, the first batch of 200 pieces produced by Hanyang Arsenal were imported from Japan at a high price. The blanks used in Russia's T5000 high-precision sniper rifle were imported from the United States. (ORSIS, which makes the T5000, is privately owned, so it is not subject to restrictions in western countries.)
Era of firearms into the grooves and caliber to initiate, the interior of the barrel becomes very complex, and the bullet propellant energy release also multiplied improve (modern bullet propellant is used nitrocellulose + nitroglycerin double-base propellant), which requires the barrel has very high strength, hardness and toughness), and using casting method basically impossible to make out qualified barrel.
Barrel manufacturing can not use the conventional casting method, because the conventional casting method is to use the mold to pour out, and the gun made by this way is relatively poor in hardness and toughness, so the barrel in order to ensure quality, must use cold forging method for manufacturing.
Cold forging is usually done with a drill. This technique creates a barrel that can withstand the heavy impact of continuous firing, providing better accuracy. Cold forging technology is a great technological progress for the safety and shooting accuracy of guns, which is why cold forging technology is widely used in the manufacture of gun barrel in the world.
The barrels of most assault rifles, light machine guns and handguns are now hammered out by cold forging machines. The device is unimpressive in appearance, but highly skilled, requiring very good control, beating and rotating evenly synchronized, if the hammer head speed is not consistent, the barrel will be deformed, not a regular round shape.
The production and manufacturing process of the barrel: the blanks are cast and forged into bars in the iron and steel factory, and the internal pores are removed, and then sent to the munitions factory for subsequent processing. After receiving the steel rods, the arsenals cut them into sections, remove the defective skins, and then punch through holes in the center of the rods with a deep hole drill. (We recommend you to pay attention to the "mechanical Engineer" public account, the first time to master dry goods knowledge, industry information)
A steel inner core with the same grooves as the rifling is then passed through, and one end is stuck to the chuck of the cold forging machine. Four brass hammerheads are used to evenly strike the blank to lengthen it while the cold forging chuck is rotated at a slow speed. Finally, the barrel also needs to polish the internal and external surface, chrome plating and other surface treatment, to meet the use requirements.
In this way, the processed barrel not only has smooth inner wall, uniform size and uniform rifling, but also has extremely high overall mechanical strength and surface hardness. Only proper surface roughness and rifling depth spacing can fully control the rotation and injection direction of bullets and improve shooting accuracy.
In a word, modern firearms manufacturing seems simple, actually need to complete large industrial base to support, can manufacture guns of the world's countries still is one of the few industrial powers, manufacturers are also well-known enterprises, with a history of one hundred other countries want to mass manufacturing performance is stable, good quality of firearms to undergo a long process, especially need to craftsmen of the spirit of we used to say.