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Jacketed Bullets

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Copper alloy jacketed bullet

© 2005-2007 Alliant Techsystems Inc

Bullets with metal jackets largely replaced plain lead bullets at about the same time that smokeless propellants replaced black powder in the majority of rifle ammunition. The higher pressures and temperatures produced by smokeless propellants were more than plain lead could support. This was overcome by adding an outer skin of harder metal to lead bullets.

Since pure copper is difficult to cold-work, copper alloys became the standard jacket material. Two copper alloys are prevalent in modern jackets, gilding metal (copper:zinc ratio of 95:5) and commercial bronze (copper:zinc ratio of 90:10). The choice of alloy depends on jacket thickness and the amount of work required to reach that thickness. The stronger bronze alloy is common in thin jackets, which are used to make handgun bullets.

In some parts of the world, soft steel is the more common jacket material. Steel is inexpensive, but more difficult to work. Nearly all steel jackets are treated with a rust preventative to ensure dimensional stability over time. This is typically accomplished with the application of transparent lacquers or by flash plating the steel with copper.

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