What characteristic of a semi-automatic firearm allows for rapid follow-up shots?

The characteristic that allows a semi-automatic firearm to achieve rapid follow-up shots is primarily tied to its operation, particularly through the gas-operated action. In a gas-operated firearm, a portion of the gas generated from the fired cartridge is diverted into a mechanism that cycles the action, ejects the spent shell, and chambers a fresh round automatically after each shot. This allows the shooter to focus on aiming and pulling the trigger again for subsequent shots, rather than needing to manually cycle the action as one would with a bolt or lever action firearm.

In the context of semi-automatic firearms, this automatic cycling enables the shooter to achieve a much quicker rate of fire than would otherwise be possible, making it especially useful in various shooting scenarios where speed and accuracy are critical. The efficient handling of gases and the design of the action are pivotal in minimizing the time between successive shots.