To prevent semi-auto shotgun malfunctions you must first understand the causes.
The beginning of hunting season and the start of sporting clays weather seems to lure shotguns that have not been used in a while out of the corners of closets everywhere.
Whether it is a sentimental moment where an old gun is taken afield or an "I haven't used this thing in a while" opportunity to break a few targets, these two times of year seem to be most popular for this occurrence. I know because the phone calls and customer traffic increases with shooters that have "jams" with their semi-auto shotgun.
These jams can be put in three categories. The failure to eject is when a fired cartridge case does not come out of the action. A failure to feed is when a live cartridge is not delivered from the magazine to the chamber, seated properly and ready to fire. The last category is any combination of problems that are malfunctions due to the gun improperly cycling.
To understand the causes and cures for these conditions, you first have to understand that there has been a tremendous evolution in the semi-automatic action. Different operating systems include but are not limited to: the long-recoil system of the original Browning A-5; the short-stroke piston of the Winchester 59; the gas recoil system of the Remington 1100 and the "Inertia Driven" piston style system.
Each system requires energy to push the bolt fully rearward. This stage ejects a fired cartridge casing and prepares a live cartridge from the magazine for feeding into the chamber. Energy is then used to push or pull the bolt forward, thereby pushing the live cartridge into the chamber. In each of these systems the energy to move the bolt rearward starts with the cartridge.
Gas from the burning gunpowder, recoil, pressure and momentum can all be used to force the bolt rearward. At the same time the bolt is moving rearward, it is experiencing counter-pressure that is trying to push the bolt back forward. The counter pressure is typically exerted by a spring that is either pushing or pulling the bolt closed.
The rearward and forward movement of the bolt must be full and complete for the gun to work properly. If the bolt travel is incomplete in either direction, it throws off the timing of a lot of other parts that are trying to lift a new cartridge from the magazine, eject the fired hull, feed the new cartridge and lock the bolt closed.
An example of this is the swinging saloon door. The door has spring loaded hinges that return it to center regardless of whether you open it toward the inside or outside. If you forcefully push the door all the way open you will have time to step through before the door closes. If you half-heartedly push the door with minimal force it will snap back and hit you before you make it through the doorway. In the latter, you and the door are out of synch or out of "timing."