Jacketed bullet
A jacketed bullet is a bullet made up of a core (usually made of lead, hard metal or even tungsten or plastic) and a jacket made of a harder metal alloy. However, the coat must be softer than the barrel. Some types of small-caliber lead bullets are only externally copper-plated.
In earlier times, as well as today, the cheap lead is often used as a material for projectiles, both for slingshots and for firearms .
Nowadays, the lead is usually placed in a jacket made of a copper alloy (e.g. tombac ), since in ammunition with higher ballistic performance a lead bullet can no longer follow the twist in the barrel due to its low hardness and the low melting temperature of the lead. It would be driven through the rifled barrel without being set in the necessary rotation, with parts of its surface being sheared off the track profile. The barrel would "remain" and thereby undesirably decrease in caliber diameter given a high rate of fire. Incidentally, after leaving the barrel, a lead bullet would not be able to withstand the high speeds that are usual with powerful cartridges and could burst in flight due to centrifugal force . In addition, ammunition with jacketed bullets is of course less sensitive to handling than those with pure lead bullets.