Mossberg manufactures several different models of pump shotguns for sporting, law enforcement and military use. The pump guns -- such as the Model 88 -- are based upon similar designs that allow field stripping for cleaning and lubrication. The Model 88's forend slide is removed for cleaning, repair or replacement.
Tilt the gun to the side and examine the magazine for shells. Determine that the shotgun is empty and safe to handle. Push the slide release forward. Pull the forend slide back to access the firing chamber; check for a round of ammunition.
Move the forend slide halfway forward. Locate the knurled nut on the end of the magazine tube; turn it to the left to loosen and remove it. Guide the ring on the base of the barrel off the magazine tube. Pull the barrel forward and out of the of the receiver.
Push the rear retaining-pin from the shotgun receiver using a punch and hammer. The pin is located just above the trigger assembly.
Pull the trigger assembly down and out of the receiver. Pull the cartridge interrupter down and out of the receiver, followed by the cartridge stop.
Turn the shotgun so that the bottom of the receiver is facing up. Insert your fingers to grasp the bolt; slide it to the rear of the receiver. Pull the bolt -slide out of the receiver.
Return the Mossberg to its side. Grip the slide and pull it forward, away from the receiver. Guide the two side-rails out of the receiver; pull the forend slide off the magazine tube.