The F1 model (adopted by the French Army and still in use today, making up the bulk of FAMAS production) has a 1:12″ twist to its rifling, effectively limiting it to 55 grain projectiles – and it also requires steel-cased ammunition to run reliably. The FAMAS uses a lever-delaying system, which allows a very simple bolt and action mechanism. The FAMAS is interesting mechanically, as it is one of very few production delayed-blowback rifle designs (the other common one being the CETME/HK series). In French service, the FAMAS was also made the formal replacement for both the MAS-49/56 rifle and the MAT-49 submachine gun, thanks to its compact nature.

Bullpup rifles offered a short overall length without sacrificing barrel length, an advantage that seemed quite valuable for troops who were to spend significant amounts of time in vehicles, where space is at a premium. It was adopted by France in 1978 at right about the same time as the Steyr AUG was being adopted by the Austrian military. The French FAMAS was one of the first bullpup rifles to be adopted and built in large numbers by a military power.