The FAL has a gas-operated action, driven by a short-stroke, spring-loaded piston housed above the barrel and the locking mechanism is a tilting breechblock. To lock, it drops down into a solid shoulder of metal in the heavy receiver. 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. The FAL's magazine capacity ranges from 20 to 30 rounds. In fixed stock versions the recoil spring is housed in the stock, while in folding-stock versions it is housed in the receiver cover, necessitating a slightly different receiver cover, recoil spring, bolt carrier and a modified lower receiver for the stock. FAL rifles can be manufactured in both light and heavy-barrel configurations, with the heavy barrel intended for automatic fire as a section or squad light support weapon. Heavy barrel FALs are equipped with bipods. The FN FAL has relatively light recoil, due to the gas system being able to be tuned via a regulator, which allows bleeding of excess gas to decrease recoil. In full automatic mode, however, the shooter receives considerable recoil and the weapon climbs off-target quickly, making automatic fire only of marginal effectiveness.
Prototypes were made compatible with the 6.5x51 FAR, 7x43 British and 7.65x53 Belgian Mauser for comparison and export testing. Belgian FALs are chambered for 7.65x53 and Dutch FALs are chambered for 6.5x51 FAR.
Production Models:
FAL 50.61 – standard rifle
FAL 50.62 – paratrooper version with folding-stock, shorter 458 mm barrel and folding charging handle
FAL 50.63 – modified 50.62 with shorter 436 mm barrel, the upper receiver is not cut for a carry handle and the bolt stop device is absent.
FAL 50.64 – folding-stock, standard barrel length, Hiduminium aluminium alloy lower receiver
LAR 50.41 – heavy barrel for sustained fire with 30-round magazine as a squad automatic weapon, has a synthetic buttstock,
LAR 50.42 – modified 50.41 with wooden buttstock
Calibre: 6.5x51 FAR or 7.65x53 Belgian Mauser or 7x43 British
Action: gas-operated, tilting breechblock
Length: 1.1m, 0.53m barrel
Weight: 4.45 to 5.15 kg
Magazine: 20-round magazine
MV: 823m/s
ROF: 600 rpm (cyclic)
Effective range: 800m depending on sights
Sights: iron sights