Semi-automatic gas-operated shotgun

A semi-automatic, gas-operated shotgun having a side-loading port, lower barrel configuration with bottom shell ejection. Gas exit ports on the barrel operate a piston which actuates a connecting rod assembly rearwardly. The rearward movement of the connecting rod assembly will compress a recoil spring and cycle the next shell into the chamber from a shell space in the carrier above the breech. The bolt assembly has upper and lower bolt members. Locking lugs on the opposite sides of the lower bolt are released by rearward movement of the upper bolt member. Shell guide retainer pins are located on the lower bolt member to assist in removing a spent shell. The modular trigger assembly has a hammer which is rotated rearwardly by the lower bolt and which returns to a "short lock time" position held ready to fire by a sear. The barrel has extensions to stop the front of the shell from passing through and out the bottom ejection port upon loading and to guide and help deliver the shell into the barrel chamber.