In the late 1950s, France was still part of the NATO integrated military structure. When the 7.62x51mm cartridge was adopted as standard for the alliance, France looked to be in a good position to simply convert their MAS 49-56 rifles to use it. After all, the 7.5mm cartridge the rifle was designed for was very similar to the new NATO round. After several years of trials, however, the project was dropped as impractical. It turned out that the much different pressure curve of the 7.62mm round would require significant redesign of the MAS rifles. They suffered from poor extraction, broken parts form high bolt velocity, and other issues (not coincidentally, the exact same problems reported with the 308 MAS 49-56 rifles imported by Century...). The St Etienne factory only made a total of 150 of them in 7.62x51mm before the project ended.