Shell casings
Modern bullets (fixed-loaded bullets) are composed of warheads + shells, which are generally wrapped in the core of the shell and then stuck to the mouth of the shell, and the shell includes the propellant that pushes the warhead and the primer that ignites the propellant.
Bullet profile view
The role of the shell casing is mainly to jam the warhead, store the propellant, and carry the primer. After the bullet fires the primer to ignite the propellant, the pressure released by the rapid combustion of the propellant will push the bullethead into the chamber and at the same time cause the shell to expand slightly, which is to make the second half of the entire bullet form an airtight with the barrel, allowing the high-pressure gas to push the warhead forward. After the high-pressure gas is released from the front of the muzzle with the warhead, the elasticity of the metal will slightly restore the expanded shell, so under normal circumstances, the shell can be successfully disemboreed.
When the quality of the shell itself or the proportion of the amount of propellant is unreasonable or the quality of the warhead is problematic, in some cases, it will also lead to excessive expansion of the shell and cannot be restored, in this case, the shell will be tightly stuck in the tail of the barrel and cannot complete the normal disemborement. Mass-produced conventional bullets generally do not have such low-level and serious quality problems, and manual reloading bullets are more likely to cause such problems because of the above various mistakes.
Bullet jam picture
Distinguished from the neck of the shell (the position of the jammed warhead), it can be divided into bottleneck type and straight wall type. The bottleneck type is the general common rifle bullet shell shape, and there is a tapered expansion shape after the warhead and the shell are joined, and the shell shell without this cone-shaped expansion shape design, or the shape is not obvious, it can be classified as a straight-wall shell, which is relatively more common in pistol bullets.
Contrast of different neck bullets
One of the reasons is that often the rifle barrel needs to withstand a greater chamber pressure - because the high-pressure gas needs to push the bullet, but also needs to push the bolt with the spring to complete the disemboweling and reloading, so the breech tube will be thicker, and for many reasons such as lethality, the bullet head of the rifle bullet also needs to be longer. The bolt re-entry of the pistol generally only needs the spring to complete. Of course, these two are only relatively common, not completely absolute.
The shell can also be divided into five types according to the shape of the tail bottom plate: shrinkage, edgeless, semi-flange, flange and belt. The so-called flange, no edge or shrinkage edge refers to the relationship between the diameter of the shell bottom plate and the diameter of the shell, in terms of the shrinking edge bottom plate, the diameter of the bottom plate edge is significantly smaller than the diameter of the shell body; the edgeless bottom plate refers to the diameter of the bottom plate edge and the diameter of the shell body are similar; the diameter of the semi-flanged bottom plate edge is significantly greater than the diameter of the shell body, but there is still a shell groove; the diameter of the edge of the flanged bottom plate is very obviously larger than the diameter of the shell body, and there is no shell groove design; the belt type except for the bottom of the similar unconnected bottom plate, There is also a band of rings on the shell in front of the shell groove.
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