FAL operates by means of a gas-operated action very similar to that of the Russian SVT-40. The gas system is driven by a short-stroke, spring-loaded piston housed above the barrel, and the locking mechanism is what is known as a tilting breechblock. To lock, it drops down into a solid shoulder of metal in the heavy receiver much like the bolts of the Russian SKS carbine and French MAS-49 series of semi-automatic rifles. The gas system is fitted with a gas regulator behind the front sight base, allowing adjustment of the gas system in response to environmental conditions. The piston system can be bypassed completely, using the gas plug, to allow for the firing of rifle grenades and manual operation. FAL's magazine capacity ranges from 5 to 30 rounds, with most magazines holding 20 rounds. In fixed stock versions of the FAL, the recoil spring is housed in the stock. However, in folding-stock versions, it is housed in the receiver cover, necessitating a slightly different receiver cover, recoil spring, and bolt carrier, and a modified lower receiver for the stock.
FAL rifles have also been manufactured in both light and heavy-barrel configurations, with the heavy barrel intended for automatic fire as a section or squad light support weapon. Most heavy barrel FALs are equipped with bipods, although some light barrel models were equipped with bipods, such as the Austrian StG58 and the German G1, and a bipod was later made available as an accessory.
Among other 7.62×51mm NATO battle rifles at the time, the FN FAL had a relatively light recoil due to the gas system being able to be tuned via regulator in fore-end of the rifle, which allowed for excess gas which would simply increase recoil to bleed off. In fully automatic mode, however, the shooter receives considerable abuse from recoil, and the weapon climbs off-target quickly, making automatic fire only of marginal effectiveness. Many military forces using FAL rifles eventually eliminated full-automatic firearms training in the light-barrel FAL
FAL was nicknamed "The right arm of the free world" because it was widely used by NATO countries and American/European-friendly nations.
The British version of FAL, the L1A1 Self-Loading Rifle had removed the automatic fire function. During the Falkland War in 1982, the British soldiers preferred to use the original version of FAL which looted from their Argentine opponent.
