Everyone who saw ammunition for domestic handguns should have paid attention to the fact that the junction between the bullet and the sleeve of many cartridges is painted in some strange red paint. Why is this done and what does such a “symbol” mean? Let's try to understand this issue. In fact, the red stripes are not at all what they seem at first glance.
So, you can see a similar color on most cartridges, but still not on all. And it’s worth starting with the main thing - the joint between the bullet and the sleeve is not painted. It's varnished. Actually, not paint, but varnish is applied to the elements of the ammunition. More specifically, it is zaponlak from the German word "Zaponlack". At one time, he came to replace the better, but much more expensive shellac. Interestingly, in the 20th century, zaponlak was used far from only in weapons. For example, the beautiful half of humanity used it for varnishing nails.
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But why do you need to varnish the joint between the bullet and the cartridge case? In fact, not only he is varnished on ammunition, but also another non-hermetic place - the junction of the cartridge case and primer, the very one on which the striker of the firearm hits before the shot. As you might have guessed, varnish is applied with one sole purpose - to increase the tightness of the design of the ammunition. So that the gunpowder inside does not deteriorate and does not become damp. And first of all, zaponlak is used to protect against water. Also, in some cases, zaponlak mixed with dyes can be used to mark different types of ammunition.
Recipes for zaponlak can be different. However, most often it is a clear solution of nitrocellulose prepared in an organic solvent in diethyl ether, acetone or ethyl acetate. The varnish itself is transparent. This or that color, for example red, as on a cartridge, it is given special dyes. As already noted, zaponlak is used far not only in weapons business. In general, this is a fairly popular substance when working with metals. Until the mid-1930s, it was also widely used in the automotive industry. Until now, it is used in the manufacture of Christmas decorations. It is also actively used in entomology, although purely transparent versions of varnish are used there to fix insect samples in books.
In continuation of the topic, read about why did sailors knit in 1917 machine-gun belts on the chest.
Source: https://novate.ru/blogs/100622/63226/