A gas flow volume control apparatus includes an adjustable gas block and a securing member as the securing member fixes the adjustable gas block onto a barrel of a firearm. The adjustable gas block is in fluid communication with the barrel so that generated gas of a propelling bullet can be recycled within a gas-operated reloading system. The generated gas is rerouted from the barrel to the gas-operated reloading system through a gas flow channel and a gas-tube channel of the adjustable gas block. An adjustment channel of the adjustable gas block also allows a user to control the rerouted amount of generated gas in order to optimize the performance of the firearm.