The Galil series of rifles are selective fire weapons operated by a Kalashnikov-pattern gas-driven piston system with no regulator. The weapon is locked with a rotary bolt with two locking lugs that lock into recesses milled into the receiver.
When fired, a portion of the propellant gases are evacuated into the gas cylinder through a 1.8 mm (0.07 in) port, drilled at a 30° angle in the barrel, and a channel in the gas block. The high-pressure gases drive the piston rod (which is attached to the bolt carrier) rearward. During this rearward movement, a cam slot machined into the bolt carrier engages a cam pin on the bolt and rotates the bolt, unlocking the action. The arrangement of parts on the bolt carrier assembly provides for a degree of free travel, allowing gas pressure in the barrel to drop to a safe level before unlocking. To the immediate rear of the chrome-plated piston head is a notched ring which provides a reduced bearing surface and alleviates excess gas build-up. As the bolt carrier travels back, it compresses the return spring guided in a hollowed section of the bolt carrier and the return energy contained in the spring drives the moving assembly back forward, stripping a new round from the magazine and locking the action. The cocking handle is attached to the bolt carrier on the right side of the receiver and reciprocates with each shot; the handle is bent upwards allowing for operation with the left hand while the shooting hand remains on the pistol grip.
The Galil is hammer-fired and has a trigger mechanism patterned after the trigger used in the American M1 Garand. The rifle's fire selector lever is on the right side of the receiver and is similar in design to the one used in the AK; it is simultaneously the manual safety. The selector's uppermost position, marked "S" ("safe") disables the trigger and covers the cocking handle slot, inhibiting the ingression of environmental debris into the receiver, but allowing the bolt to be retracted enough to check the chamber. Unlike the AK, the Galil includes a selector switch on the receiver's left side—above the pistol grip—intended to be manipulated by the thumb of the shooting hand. This switch has three positions: "R" (British terminology for "repetition" or semi-automatic fire); the middle position, "A", produces fully automatic fire; and pushing the lever fully forward will activate the safety.
The Galil prototypes used a stamped and riveted sheet metal steel receiver, but due to the higher operating pressures of the 5.56x45mm cartridge, this solution was discarded and the designers turned to a heavy milled forging. As a testament to its heritage, early prototypes were fabricated using Valmet Rk 62 receivers manufactured in Helsinki. All exterior metal surfaces are phosphated for corrosion resistance and then coated with a black enamel (except for the barrel, gas block and front sight tower).
The weapon is fitted with a high-impact plastic handguard and pistol grip and a side-folding (folds to the right side) tubular steel skeleton stock. The rifle can be used with a sound suppressor. The weapon features a bottle opener and wire cutter built into the bipod. The bottle opener feature was included to prevent damage to magazines being used to open bottles, due to the large civilian reservist components of the IDF. Wire cutters were included to reduce the time necessary for IDF troops to cut down wire fences common to rural areas in Israel.