Sweden developed, adopted, and produced a new self-loading rifle during World War Two. The process began in 1938, with an attempt by the state rifle factory to convert Swedish Mauser bolt actions into semiautomatic; that did not go well. Trials for a ground-up semiauto followed shortly thereafter, with the two finalists being the Pelo rifle from Finland and a design by Erik Eklund of the C.J. Ljungmans Verkstäder, a company that made gas pumps and had no prior small arms experience. Eklund focused on making his rifle as simple as possible, and created a direct gas impingement system with a tilting bolt and a rather unique method of operation. It was chambered for the 6.5x55mm cartridge, with a detachable 10-round magazine (which was intended to be reloaded with stripper clips).

The rifle went into production in 1942, and by 1944 rifles were being delivered to the military. They were never a complete replacement for the various patterns of Swedish Mauser, instead being used to supplement squad firepower. In 1953 a major refit program was put in place, making a number of changes and creating the Ag m/42B pattern. Those rifles remained in use until eventually replaced by the AK4, the Swedish model of the G3 rifle from Heckler & Koch.