The MAS 49/56 is a semi-automatic gas operated rifle in 7.5 caliber. It is fed by a 10 round detachable magazine. The "MAS" in the MAS 49/56 designation is an abbreviation of Manufacture d'Armes St. Etienne which is one of several government owned arms factories located in France. The MAS 49/56 is an improved version of the MAS 49. The MAS 49/56 was introduced in 1957 and brought with it the lessons learned by the MAS 49 from service in places such as Algeria, Indochina, and the Suez Crisis. The MAS 49/56 was both shorter and lighter then the MAS 49. This change was done to improve the mobility for mechanized and airborne troops The MAS 49 had a spike bayonet which was changed to a knife bayonet for the MAS 49/56. The MAS 49 had a built in grenade launcher that was changed to a combination rifle grenade launcher and compensator. In 1980 the MAS 49/56 ended production and was replaced with the 5.56 x 45 mm NATO caliber FAMAS bullpup assault rifle. FAMAS is an abbreviation of Fusil d'Assaut de la Manufacture d'Armes de Saint-Étienne or Saint-Étienne arms factory assault rifle. The MAS 49/56 was finally phased out totally from French service in 1990.
The French 7.5 caliber ammunition is quite expensive here in the states. So some of the MAS 49/56 rifles that are in collectors hands here in the U.S. have been sent to the gunsmith and re-chambered to fire the more common 7.62 x 51 mm NATO round. This conversion has been plagued with problems which includes both jams and misfires. The reason for these problems is that when the conversion is done, the barrel length is shortened a tad to allow the new cartridge to be chambered. By doing so, this brings the gas vent closer to the chamber which creates a much higher stress on the bolt carrier.
Another problem for collectors of the MAS 49/56 is that some of the commercial 7.5 X 54mm ammunition that was made in countries other than France have been known to produce a burst of two, three or more rounds being fired with one trigger pull. This problem can be easily fixed by replacing the original heavy military firing pin with a lighter titanium firing pin. It has been found that this ammunition that was not made in France has a primer that is much more sensitive. With the heavy action of the bolt, the original firing pin had enough inertia to detonate the ammunition with sensitive primers.