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Home > Propellants, Firearms, and Ammunition Development > Ammunition > Projectiles > Jacketed

The material surrounding a bullet is referred to as a bullet jacket. The first bullet jackets were comprised of cloth patches applied to round balls. They were intended to engage the rifling, causing the bullet to spin. Early bullet jackets also included paper that engaged the shallow rifling of certain firearms (notably single-shot rifles and target arms).

As smokeless propellants evolved, so too did the use of metallic bullet jackets. Compared with black powder, smokeless propellants produced higher velocities, pressures, and temperatures, and increased frictional forces. This could cause partial melting of lead bullets in the bore and sufficient heat to melt the bearing surface (the area of the bullet that engages the rifling).

Metal jackets were used to

  • preserve the physical integrity of the bullet,
  • facilitate engagement of the rifling,
  • allow rapid fire of cylindrical bullets.

There are two primary types of metal jacketed bullets, semi- and full. Semijacketed bullets are typically used in hunting game because they provide controlled expansion. The full metal jacket bullet became the standard for military ammunition because the rigid tip feeds reliably into the chamber of semi- and fully automatic firearms.

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