Which firearm design utilizes a gas piston in the unlocking phase of the cycle of operations?

The correct answer is based on the function and mechanics of the long stroke and short stroke gas piston systems, which play a crucial role during the unlocking phase of the cycle of operations in a firearm.

In a gas piston system, when the firearm is fired, gas from the fired cartridge is diverted through a port into a piston. In a long stroke system, the piston moves a considerable distance and directly interacts with the bolt carrier or bolt, effectively unlocking and cycling the action. This allows for reliable functioning as the piston and bolt are closely connected during the gas operation, ensuring that energy is effectively transferred to cycle the action.

In a short stroke system, although the piston moves a shorter distance before it imparts its energy to the bolt carrier, it still plays a significant role in the unlocking phase by initiating the movement required to engage the cycling process. Each of these designs leverages the energy from the expanding gas to unlock and cycle the action, ensuring reliable operation and reloading after discharging a round.

The other options do not incorporate a gas piston in the unlocking phase. Recoil-operated systems rely on the inertia of the sliding mass to unlock the action, while direct impingement systems use gas directed straight into the bolt carrier to cycle the action without a