What are the three basic gas-operated designs?

The three basic gas-operated designs are indeed identified as Short Stroke, Long Stroke, and Direct Impingement. Each of these systems functions using gas from the ignited propellant to cycle the action of the firearm, but they achieve this in distinct ways.

In a Short Stroke gas system, a portion of the gas is redirected to operate a piston that moves a short distance before returning rearward to cycle the action. This design allows for more control over the operation since the piston is not directly acting on the bolt carrier.

The Long Stroke gas system operates on a similar principle, with the main distinction being that the piston moves a longer distance, directly attached to components that cycle the action of the firearm. This design is often simpler and more robust, leading to improved reliability in some applications.

Direct Impingement utilizes gas that is bled off from the barrel and directly affects the bolt carrier group. This design is known for its lighter weight and fewer moving parts compared to the piston-operated systems, but it can lead to a greater accumulation of carbon and fouling within the action.

These distinctions highlight the attributes of each design and their suitability for different firearm applications, which is critical knowledge for understanding gas-operated firearm mechanisms.