How a RN Five-Seven works

The FN Five-seven, trademarked as the Five-seveN, is a semi-automatic pistol designed and manufactured by Fabrique Nationale d’Armes de Guerre-Herstal (FN Herstal) in Belgium. The pistol is named for its 5.7-mm (.224 in) bullet diameter, and the trademark capitalization style is intended to emphasize the manufacturer's initials—FN