Due to the lack of copper reserves, China has long mainly used steel bullet shells. The copper content in China's crust is only 0.01%, far lower than the 8.1% of aluminum and 5.06% of iron. Although the price of copper is not a precious metal, it is widely used in all walks of life and is in high demand, so copper is expensive. Making cartridge cases from copper cost enormously in warfare, with 12.7 mm large-caliber machine gun bullets, for example, costing up to $4.2 per round. In battle, hundreds or even thousands of rounds of ammunition are consumed, even if the intensity is low. This made the United States deeply aware of the high cost and limited resources of copper shells.
In addition, copper shells are heavier, with a density of 8.9 grams per cubic centimeter, which is higher than iron and aluminum. With the development of individual armor, more bullets are needed to damage enemies. In the wars in Afghanistan and Iraq, U.S. soldiers often carried more than 50 kilograms of ammunition, a large part of which was copper-shelled ammunition, which increased the fatigue of soldiers, reduced mobility, and increased the difficulty of logistics and supply. The adoption of new lightweight ammunition reduces the burden on soldiers even if the amount of ammunition remains the same.
In contrast to copper shells, the new lightweight ammunition still uses a standard warhead, gunpowder and primer. The core lies in the manufacturing process of polymer cartridge shells, which use injection molding to automatically seal the mouth of the cartridge case, without the complex process of traditional metal cartridge shells. Polymer shells are lighter than copper shells, lighten the burden on soldiers and are cheaper. Bullets made of polymer cartridge cases can be produced faster, which helps to ensure the supply of ammunition to the army. This new type of bullet retains the shape of the cartridge case after firing, does not expand and tightly binds to the chamber, reducing the wear and tear of the chamber. In addition, the polymer has good thermal insulation and does not absorb the heat generated when fired, helping to prevent the cartridge case from overheating when firing continuously, reducing the risk of burns to the shooter.
Bullets with polymer cartridge casings have been popular in the civilian firearms market in the United States for many years. Currently, both the US Marine Corps and the US Army are investing heavily in the development of new lightweight ammunition. According to the requirements of the US military, the new lightweight ammunition should be finalized in 2022, and in 2023 it should be officially equipped with combat units. China needs to be vigilant against the elimination of copper shells and look for better materials for shells, otherwise it will distance itself from the world's advanced level.