US Patent 10890391 Anti-rattle biasing devices for firearms

An anti-rattling biasing device for firearms includes a spring configured to exert a biasing force against an upper receiver and a lower receiver of the firearm. The biasing force urges the upper and lower receivers firmly into contact with the pins that couple the upper and lower receivers, inhibiting small back and forth movement between the upper and lower receivers and thereby reducing or eliminating rattling of the upper and lower receivers when assembled together.