What is the Sears model number? Some of the gas operated shotguns are
adjustable for different power level ammunition. Some have o-rings that
can wear and cause short cycling.
Exactly what does it do? The bolt doesn't move at all? It moves, but not
far enough to eject the empty? It ejects the empty but doesn't load
a new round?
Agreed--try it with some magnum shotshells--but it should be possible
to make it work with standard field loads.