Semi-automatic shotgun

A semiautomatic shotgun for use with first and second shotgun shells having a blunt front end, the semiautomatic shotgun comprising:

• a lower receiver from the AR-10 family of firearms;
• an upper receiver mounted to the lower receiver;
• a barrel dimensioned and configured to receive such shotgun shells into a chamber, the barrel having a distal muzzle end and a proximal end, the proximal end having thereon a barrel extension mounted to the upper receiver;
• a bolt slidably mounted and dimensioned and configured to slide in and out of the chamber across the open top end of the magazine in an upper receiver main bore;
• a bolt carrier mounted in an upper receiver bore so as to be slidable, the bolt extending into the bolt carrier;
• a direct impingement gas system in which gas from such first shotgun shell may cause extraction and ejection of such first shotgun shell and feed of such second shotgun shell;
• the direct impingement gas system including at least a gas port having upper and lower ends, the gas port passing through the barrel, the gas port having an angle to the barrel of greater than 90 degrees whereby the gas port lower end is slightly closer to the distal muzzle end while the gas port upper end is slightly closer to the proximal end;
• a low profile gas block mounted to the barrel at the gas port upper end;
• a gas tube elevated above the barrel, the gas tube connecting at a first end the gas port upper end and at a second end a gas key;
• the gas key having an aperture therethrough from the gas tube to a gas impingement chamber;
• the gas impingement chamber located within the bolt carrier, a first side of the gas impingement chamber being the bolt;
• the bolt slidably mounted within the bolt carrier such that the bolt may move relative to the bolt carrier, whereby the gas impingement chamber may change volume, and further whereby a pressure increase within the gas impingement chamber may cause the bolt and the bolt carrier to move relative to one another;
• the bolt having a bolt tail projecting from the first side of the gas impingement chamber;
• a spring mounted upon the bolt tail within the gas impingement chamber;
• a cam pin passing through the bolt, the cam pin having a first end slidably mounted within an angled slot whereby when the bolt moves backward it is impelled to rotate due to the motion of the cam pin the angled slot;
• a plurality of locking lugs on a front end of the bolt, the locking lugs dimensioned and configured to engage to the barrel extension when the bolt is in a first firing position, and configured to rotate and disengage from the barrel extension when the bolt rotates and moves backward into a second position;
• whereby when the locking lugs disengage, a gas pressure in the chamber may cause rearward motion of the bolt carrier.