A Mossberg heat shield is designed to fit on plain (without rips) shotgun barrels for the Mossberg model 500 and 590 line of pump action shotguns. Mossberg only produces heat shields for its 12-gauge shotguns. Heat shields are generally associated with tactical shotguns — the style that law enforcement and military agencides widely use. The purpose of a heat shield is to help dissipate the heat generated when the weapon is fired to keep the barrel as cool as possible. Before installing a heat shield on your Mossberg shotgun, check that the weapon is unloaded.
Place the shotgun barrel up with the action open. Unscrew the cap at the end of the tube magazine, just beneath the barrel. When you remove the cap, the magazine spring will emerge; leave it in place. Lift the barrel off the shotgun.
Use a small adjustable wrench to unscrew the brass front sight. Carefully slide the end of the heat shield over the barrel so it seats on the end of the barrel.
Position the screw guides between the interior of the forward mounting bracket. Slide the retention screws through the guides until they emerge on the other side of the mounting bracket. Put nuts on the ends of the retention screws and tighten them with an Allen wrench.
Put the brass front sight back on, return the barrel to its original position and place the end cap back on the tube magazine.