Adjustable Volume Piston System

An adjustable volume gas block for a firearm having a barrel and a gas pin, comprising:

• a plug having a bore;
• the plug inserted into the gas block bringing the bore in pneumatic communication with the barrel;
• the gas pin biased against the bore forming an enclosed chamber;
• and
• wherein when the firearm is fired, gas enters the enclosed chamber, forcing the gas pin away from the bore;
• and
• wherein as the gas pin moves away from the bore a port is exposed allowing the gas to exit the gas block.

A method of adjusting the timing of an automatic reloading firearm having a gas pin and a barrel, comprising the steps of:

• providing a gas block having a chamber;
• installing a gas block on the barrel;
• providing a pneumatic communication in the gas block between the chamber and the barrel;
• providing a plug having a bore;
• inserting the plug into the chamber;
• inserting the gas pin into the chamber opposite the plug;
• and
• firing the firearm, thereby causing a delay in the automatic reloading action of the gas pin.