The Chassepot, officially known as Fusil modèle 1866, was a bolt-action military breechloading rifle. It is famous for having been the arm of the French forces in the Franco-Prussian War of 1870–1871. It replaced an assortment of muzzleloading Minié rifles, many of which were converted in 1864 to breech loading. An improvement to existing military rifles in 1866, the Chassepot marked the commencement of the era of modern bolt action, breech-loading military rifles. The fusil Gras modèle 1874 was an officially adopted successor to the Chassepot. Although based on and frequently converted from existing Chassepot rifles, it was designated a new model and adopted as a separate rifle firing a metallic cartridge.