5.56 refers to the 5.56 NATO (5.56x45mm) rifle cartridge, widely used in AR-15 platforms for military, law enforcement, and civilian applications. While not a manufacturer, many firearms companies produce 5.56-specific parts, including barrels, upper and lower receivers, bolt carrier groups, magazines, and complete rifles or pistols. These components are compatible with AR-15 rifles and other 5.56 platforms, making 5.56 a popular choice for shooters and builders seeking reliable, high-performance solutions for target shooting, hunting, and tactical use.
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