How a FN FNC works

The rifle was developed between 1975–1977 for NATO standardization trials. The rifle’s design is based on the FNC 76 prototype, which itself originated from the commercially unsuccessful FN CAL rifle. This prototype was soon withdrawn from the NATO competition after performing poorly due to its rushed development. Later trials for the Swedish Armed Forces held between 1981–1982 using updated prototypes proved the utility and efficiency of the design, impressing both the Swedish military and Belgian Army staff back at home. The FNC was finally adopted by the Belgian Armed Forces in 1989, as a service-wide replacement for the 7.62×51mm NATO FN FAL, after having been issued in small numbers to airborne infantry units for several years.

Indonesia purchased approximately 10,000 rifles in 1982 for its air force, and later acquired a license to manufacture these rifles for all branches of the armed forces. These are built by the Indonesian firm PT Pindad as the Pindad SS1 and Pindad SS2. A version of the FNC adapted for arctic conditions was adopted in 1986 as the standard service rifle of the Swedish Armed Forces (with the designation Ak 5) and is used in relatively small numbers by a number of other armies and police organizations.

The FNC is a selective fire weapon that uses a gas-operated long-stroke piston system and a rotating bolt locking mechanism equipped with two locking lugs that engage corresponding recesses in the barrel extension. The bolt is rotated and unlocked by the interaction of the bolt's cam pin with a camming guide contained in the bolt carrier. Overall, the mechanism strongly resembles that of Kalashnikov rifles, but adapted to more advanced design and production methods. The rear part of the cocking handle slot, cut in the upper receiver for the cocking handle, is covered by a spring-loaded cover which automatically opens by the handle when it goes back and automatically closes the opening when the cocking handle returns forward.

The spring extractor is located inside the bolt head, the ejector is fixed and riveted to the inside of the receiver housing. The FNC uses a 2-position gas valve, a hammer-type firing mechanism and a trigger with a fire selector switch that is simultaneously the manual safety, securing the weapon from accidental firing. The selector lever is located on the left side of the receiver and has 4 settings: "S" - weapon safe, "1" - single fire mode, "3" - 3-round burst, "A" - continuous (automatic) fire.

The FNC's barrel features a flash suppressor that is also used to launch NATO standard 22mm rifle grenades (only the standard rifle model has this capability). The gas block contains a gas valve setting that is used to isolate the gas system, providing an increased volume of propellant required to fire a rifle grenade. The sheet-metal gas valve switch when pulled upright, acts as a V-notch sight used for aiming the rifle grenades. The piston head and extension, as well as the gas port block, barrel bore and chamber, are hard-chrome plated to minimize the effects of propellant fouling.

The rifle feeds from 30-round steel magazines that are interchangeable with magazines from the American M16 rifle (STANAG 4179 compliant). After the last round is fired, the bolt will remain closed as there is no provision for an automatic bolt hold open. However, the bolt handle can be manually worked to hold the bolt back. FNC magazines will function in AR-15/M16-type rifles but the follower will not hold the bolt open on the last round unless they have been replaced by an M16-type follower.

The plastic-coated, lightweight alloy skeleton stock folds to the right side of the receiver. A fixed synthetic (polyamide) buttstock is also available.

The upper receiver is made from stamped steel, the lower receiver, along with magazine housing, is made from aluminum alloy.

The rifle has a flip-type L-shaped windage-adjustable rear sight with two apertures with settings for 250 and 400 m, while the front sight post is adjustable for elevation. Optics such as the Hensoldt 4× telescopic sight can be attached with the use of a receiver-mounted adapter.

Standard equipment supplied with the FNC includes a spike bayonet or a variant of the American M7 blade bayonet (with the use of a lug adapter) and a sling. The rifle can be deployed with a barrel mounted bipod and blank-firing adaptor.