Why are bullets painted?

I don't know which part you mean by paint.

There are about three kinds of paints used on bullets.

The first type: the paint on the surface of the shell is mostly used on the surface of the steel shell. Its main function is to prevent the steel shell from direct contact with the outside world and protect the shell from external corrosion. Painted steel shells in China are generally green or brown, and there are also gray ones abroad.

The second type: paint inside the shell casing. There are two places that need painting, one is the joint with the warhead, which is painted internally (inner coating) and then assembled with the warhead, and then painted at the joint between the shell and the warhead (outer coating), and the other is the place where the primer is assembled. After the fire is assembled, the joints are usually painted with varnish. Their function is to prevent water vapor from entering the shell from the gap between the warhead and the primer, and to prevent the propellant/primer from deterioration and failure due to moisture.

The third type: bullet-pointed painting. Also known as color code. It is mainly used to identify the type of ammunition. The area of paint generally accounts for 1/3 or 1/4 of the warhead, such as black for armor-piercing ammunition, red for incendiary ammunition and purple for armor-piercing burning tracer. Generally speaking, color coding systems in different countries are divided into two systems: the United States and the Soviet Union.

Generally speaking, bullets, or the paint on the surface of ammunition, have their own uses, all for the good preservation and convenient use of bullets, and are not wasted ~