What is suppose to happen is that the first cartridge in the magazine is suppose to rest against the primary cartridge stop on the left side of the gun. As you pump the gun, the secondary cartridge stop on the right moves in and the primary stop releases the first cartridge onto the carrier. The second cartridge is caught by the secondary stop. As you close the action, the carrier pushes the first cartridge up and into the chamber as the primary stop is activated and the secondary cartridge stop releases the second cartridge onto the primary cartridge stop.
Given that information, see if you can determine whether the primary or secondary isn't working.
MSSA Life Member