Paintball shotgun.. hmmm.
Humor me for a minute... Take a paintball, double its size and instead of filling it with paint, fill it with X-number of smaller paintballs.
First problem I could see is the main paintball would have to be very thin and designed so that the force of the air would break it apart so the "shot" would be dispersed.
Another option would be to skip the whole large paintball and dump a bunch of smaller balls into the breach, but how would you keep them from rolling out the front of the barrel..?
Yes, I understand this may not be practicable but in CQB that could be a blast. Anyway.. Im just thinking out loud.