Always Match the Data Stamp First
Like rifles, shotguns have a data stamp usually located on the right or left side of the barrel. It indicates the gauge and maximum length of the shotshell that can be fired safely. Gauge and shell length are also shown on the shell base and box.
A magazine 'plug' is usually made of wood or plastic and is inserted in the tubular magazine to limit the number of shells a shotgun may hold. Federal law requires that the shotgun be limited to a capacity of three (3) shells (one in the chamber and two in the magazine) while hunting any type of migratory birds including doves and waterfowl.
Understanding a Smoothbore Barrel
A shotgun used for shot features a smoothbore barrel, meaning that there is no rifling. Rifles can be used for short and long distances. Shotguns are highly accurate for shorter distances.