Plastic cartridge cases are cartridge cases made of plastic. The molding of plastic cartridge cases mainly involves mold design and molding process control. These factors have a great influence on the strength, rigidity, shrinkage rate, etc. of the cartridge case, and are an important link in controlling the quality of cartridge case processing. Plastic cartridge cases can not only make bullets lighter, but also reduce production costs and use costs.

During wars, the consumption of ammunition is huge. In order to reduce the load of soldiers and increase the amount of ammunition carried, the weight of ammunition must be reduced. Starting to use plastic instead of metal to make cartridge cases can greatly reduce the weight of ammunition and the load of soldiers, and can also reduce the cost of ammunition, making it cheaper and easier to load. Early plastic cartridge cases were generally only used in blank cartridges, training cartridges or shotgun cartridges, and plastic cartridge cases can also enter the human body and cause tissue damage. Since the 1960s, foreign countries have begun to experiment with the application of plastic cartridge case technology to high-pressure automatic weapons. By the 1980s, various automatic rifles of several American companies began to be equipped with plastic cartridge cases.

The first plastic cartridge case in the world to be used in large quantities was the plastic blank cartridge developed by the Norwegian company Beckritt. Later, the Federal Republic of Germany's Nobel Dynamics also developed a plastic practice cartridge with high muzzle safety. In recent years, due to the great progress made in high-strength engineering plastic and resin-based composite materials, high-performance plastic such as nylon series, reinforced polycarbonate, polysulfone and liquid crystal polymer have appeared one after another, making the application of plastic cartridge cases in high-pressure automatic weapons possible.

Performance Research

Regarding the application of plastic cartridge cases in high-pressure automatic weapons, foreign countries have carried out research work for a period of time and have made some progress. For example, the plastic cartridge case flush-head small arrow bullet developed by the Austrian Steyr-Mannlicher Company has been tested and selected in the US ACR program. The use of plastic cartridge cases requires research on material performance, cartridge case joint technology, cartridge case molding process, etc.

The role of the cartridge case is to: combine the bullet, primer, propellant, etc. into a whole, and position the bullet in the chamber; contain and seal the propellant so that it has a specified chamber volume; seal the gunpowder gas during firing to prevent the high-temperature and high-pressure gunpowder gas from burning the chamber or rushing out from the tail of the barrel. As the plastic material of the cartridge case, it should meet the basic requirements for use: have high strength, rigidity and a certain elongation; do not burn, be non-toxic, and withstand instantaneous high-temperature impact under high-temperature and high-pressure conditions; have good anti-aging and corrosion resistance, low water absorption, and be convenient for long-term storage; do not react chemically with the propellant and have good compatibility; have good processability, low material density, small shrinkage rate during injection molding, and good dimensional stability; widely available materials and low cost. From the above, it can be seen that high requirements are placed on plastic materials in terms of use environment, processability, and economy.

Jointing technology

The shell jointing technology mainly studies the technology that meets the strength, rigidity, reliability and special requirements during the ammunition firing process. The shell joint technology of conventional bullets cannot meet the strength requirements of plastic shells under high chamber pressure, so new scheme design and research should be carried out from the joint of the whole bullet and the shell. Plastic shell buried bullet is a new joint technology. Unlike conventional bullets, its bullet is a cylinder (the bullet head is buried in the shell, and the bullet has additional auxiliary parts such as bullet cap and fixing ring in addition to the original parts).

The chamber pressure is borne by the chamber wall during firing. In addition, there is still a certain gap between the chamber and the shell, and the shell produces a certain elastic deformation under high pressure. The joint of the plastic shell should also meet the following requirements: First, the shell should have a certain rigidity when firing the primer to ensure the reliability of firing. In order to achieve this goal, metal parts are generally installed between the primer and the shell; second, the shell has a certain impact toughness and elongation, and the shell will not break when the chamber pressure reaches the peak; third, the shell can be smoothly pulled out of the chamber after shooting; fourth, the shell has good processing technology and does not produce too much stress concentration after molding.

Process Research

The molding of plastic cartridge cases mainly involves mold design and molding process control. These factors have a great influence on the strength, rigidity, shrinkage rate, etc. of the cartridge case, and are an important link in controlling the processing quality of the cartridge case. When studying a plastic cartridge case, if the same material and mold are used with different injection molding temperatures and pressures, the strength of the cartridge case will be significantly different. When the injection molding temperature and pressure are low, the cartridge case will crack under a lower chamber pressure; when the injection molding temperature and pressure are too high, the internal stress of the cartridge case is large, and the strength of the cartridge case will decrease after being placed for a period of time. Only when the injection molding temperature, pressure and mold temperature match appropriately, the cartridge case will have better strength. Among them, the plastic cartridge case of a buried bullet studied, when the chamber pressure in the closed chamber reaches 250MPa, the cartridge case basically does not crack.

The cartridge case material starts with traditional brass, and goes through the improvement process of copper-clad steel shell, steel shell, aluminum-clad steel, aluminum shell, and plastic cartridge case. The replacement of metal shells with non-metal shells represented by plastic shells is a leap forward in the history of material development.

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