Gas-delayed blowback operating system and method for AR-pattern firearms

A gas-delayed blowback firearm, comprising:

• an AR-pattern lower receiver;
• an upper receiver releasably couplable to the lower receiver;
• a barrel attachable to the upper receiver, the barrel having a cartridge chamber, an axial bore, and a barrel gas port in fluid communication with the bore;
• a bolt assembly receivable in the upper receiver and configured to reciprocate therein between a forward in-battery position and a rearward position;
• a timing block attachable to the bolt assembly;
• a cylinder housing attachable to the upper receiver, the cylinder housing having an internal gas chamber and a cylinder gas port in fluid communication with the gas chamber
• a recess defined in a forward portion of the upper receiver, the recess configured to receive at least a portion of the cylinder housing when the cylinder housing is attached to the upper receiver;
• a gas passageway defined through the upper receiver which fluidly communicates the barrel gas port with the cylinder gas port when the barrel and the cylinder housing are attached to the upper receiver;
• and
• a plunger receivable in the gas chamber and attachable to the timing block such that the plunger reciprocates with the bolt assembly when the plunger is attached to the timing block and the timing block is attached to the bolt assembly;
• wherein discharge of a cartridge received in the cartridge chamber temporarily pressurizes the gas chamber, applying a forward force to the plunger which causes the plunger to delay rearward travel of the bolt assembly until the pressure in the gas chamber decreases enough for a rearward force applied by the cartridge against the bolt assembly to overcome the forward force applied to the plunger and move the bolt assembly toward the rearward position.

An upper receiver assembly for a gas-delayed blowback firearm, comprising:

• an upper receiver releasably couplable to an AR-pattern lower receiver;
• a barrel attachable to the upper receiver, the barrel having a cartridge chamber, an axial bore, and a barrel gas port in fluid communication with the bore;
• a bolt assembly receivable in the upper receiver and configured to reciprocate therein between a forward in-battery position and a rearward position;
• a timing block attachable to the bolt assembly;
• a cylinder housing attachable to the upper receiver, the cylinder housing having an internal gas chamber and a cylinder gas port in fluid communication with the gas chamber;
• a recess defined in a forward portion of the upper receiver, the recess configured to receive at least a portion of the cylinder housing when the cylinder housing is attached to the upper receiver;
• a gas passageway defined through the upper receiver which fluidly communicates the barrel gas port with the cylinder gas port when the barrel and the cylinder housing are attached to the upper receiver;
• and
• a plunger receivable in the gas chamber and attachable to the timing block such that the plunger reciprocates with the bolt assembly when the plunger is attached to the timing block and the timing block is attached to the bolt assembly;
• wherein discharge of a cartridge received in the cartridge chamber temporarily pressurizes the gas chamber, applying a forward force to the plunger which causes the plunger to delay rearward travel of the bolt assembly until the pressure in the gas chamber decreases such that a rearward force applied by the cartridge against the bolt assembly overcomes the forward force applied to the plunger and moves the bolt assembly toward the rearward position.