When you push the spear in you push water out of the barrel via a purge valve in the handle, so that is the only effort required. The water is eliminated from the gun's interior to allow space for the gas to enter the gun. The purge valve is activated with one hand, you push the spear in with the other. That is the way the "Pelletier" works, which is the gun that the Maco2 is based on.