US Patent 9879931 Modular multi-caliber belt-fed machine guns

Various embodiments of multi-caliber machine gun systems are described. A multi-caliber machine gun system can include a receiver assembly, a first ammunition feed tray, and a second ammunition feed tray. The first ammunition feed tray can be configured to removably attach to the receiver assembly and to feed a first type of ammunition to the receiver assembly. The second ammunition feed tray can be configured to removably attach to the receiver assembly and to feed a second type of ammunition to the receiver assembly. The receiver assembly can be configured to fire the first type of ammunition when the first ammunition feed tray is removably attached to the receiver assembly. The receiver assembly can be configured to fire the second type of ammunition when the second ammunition feed tray is removably attached to the receiver assembly.