Circa 1954, Sweden was starting to look for a new self-loading rifle to adopt for its infantry. The 6.5x55mm cartridge was a good round, but the idea of having ammunition compatibility with its neighbors was appealing, and NATO was standardizing on the new 7.62x51mm round. This rifle is an experimental conversion of a Ljungman to the NATO cartridge, which included replacing the original simple gas impingement system with a short-stroke piston. It's unclear why that change was required given the successful Egyptian use of 8x57mm Mauser in the Ljungman system, but possibly it was needed in order to keep the gas block in the same place and reduce the cost of converting existing rifles should the system be adopted.