A semi-automatic rifle, also known as a self-loading rifle, is a rifle that fires one shot with every pull of the trigger. Unlike repeating rifles that require the user to manually work the action between each shot, self-loading rifles automatically chamber the next round after firing. This has historically been achieved through a variety of different methods, predominantly gas operation and recoil operation.
Self-loading rifles initially emerged in the late 19th century, with one of the first examples being designed by Ferdinand Mannlicher in 1885. Many other inventors and engineers devised their own self-loading mechanisms, and some of the earliest designs exhibited eccentricities, such as the inertia-based action employed by the Sjögren rifle. By the early 20th century, most designers settled on recoil or gas-based operation. Many of these rifles were publicized as revolutionary weapons and submitted to military testing, but failed to attract buyers, as they were considered less reliable and accurate than contemporary bolt-action rifles.
The first self-loading rifle to achieve success was the Mexican-designed, Swiss-made Mondragón M1908. Originally intended for the Mexican Army, a few thousand were sold to the German Empire during World War I and were used by aviators. Also in World War I, the French developed the RSC self-loading rifle, which saw limited combat use before the war ended.
Despite some early success during World War I, most military forces did not adopt a self-loading rifle until the 1930s and 40s. The US Army took up the M1 Garand as its standard service rifle in 1936 and it was used to great effect during World War II. The Soviets adopted the SVT-40, which inspired Nazi Germany to developed an equivalent weapon, the Gewehr 43. After World War II, France and Britain, who had not adopted self-loading rifles during the war, adopted the semi-automatic MAS-49 and L1A1 SLR respectively. But otherwise, the advent of selective-fire assault rifles rendered self-loading rifles obsolete.