shinyballs,
It sounds like someone took a good idea, didn't understand it, and created a useless product. A "dead-blow" hammer has a hollow core in the head which is partially filled with lead shot. When the hammer is swung, the shot moves to the trailing end of the head. When the hammer face strikes the target, the shot continues moving to the front of the core near the face. This serves only one purpose: it keeps the hammer head from bouncing (and it really works). It does not increase the force of the blow (as you would want it to do on a break cue), but significantly decreases the force of the blow. It sounds like your friend's cue was designed by someone who owns a hammer but had no other qualifications.