This may come as a surprise to some folks, but the first semiautomatic rifle adopted for military use was the M1908 Mondragon rifle designed in Mexico by Manuel Mondragon. He was granted a US patent on the design in 1907, and the variants of the rifle were purchased by the Mexican military starting in 1894. Mondragon’s development process began with the initial idea in 1891, and reached its peak in 1915 when the German military adopted it in 1915 as a rifle for use in observation aircraft (as the Flieger-Selbstlader-Karabiner 15, or Aircraft Self-Loading Carbine Model 1915).
The Mondragon has one particularly notable feature – a manual operation latch on the bolt handle which would cut off the gas system and make the gun into a manual straight-pull action. This was an idea in the tradition of magazine cutoffs in early bolt action rifles. Commanders and military bureaucrats were concerned about soldiers wasting ammunition through rapid fire, and wanted a way to force a slower rate of fire. The idea on the Mondragon was that the rifle would be used manually except in emergencies, at which time you could throw the switch and blaze away (at least until you emptied the 8-round magazine).
We have a new gallery of photos of a Mondragon rifle on the Mondragon page of the Vault, as well as a much-expanded history of the piece, a few photos of a 20-round box magazine, and a copy of Mondragon’s 1907 patent.