If you are having trouble with the MSG-501 staple gun, please make sure that you are applying the appropriate amount of pressure when using. The correct amount of pressure to be used while on a flat surface; holding the staple gun as the manual instructed is 55lbs. More often than not, the user is trying to squeeze the handle using the force their hand. With the Cable Boss you want to use your body weight to trigger the staple gun.
Improper care of the tool can also cause it to jam or malfunction. Tool care should always be the priority after safety.
Gardner Bender FAQ 