All models of the series are gas operated with a mechanism that noticeably reduces recoil.

[citation needed] The Sportsman 12 Auto had less costly birch stocks and less rollmarking on the gun's receiver.

These were simply cosmetic differences, and all Model 1100 parts in 12 gauge are fully interchangeable, including barrels and receivers.

[5][6] The Model 1100 bleeds off gases to operate the action through ports in the barrel near the fore end.

The gasses then drive a steel action sleeve that fits around the magazine tube and connects to the bolt carrier to the rear, ejecting the spent shell.