Good to know. I wonder if the people who did the hot glue shot/slug cartridges left an area in the bottom with just glue like my friend did with the wax. Leaving the back end lighter should allow the projectile to fly relatively straight. I can see how it might be very difficult to prevent voids in the hot glue which would leave a very unbalanced projectile. If you're talking about taofledermaus, I didn't think there was any shot in the silly putty.
Honestly, I don't expect anything to work substantially better than buck shot or slugs for defense. There's a reason the major ammunition manufacturers don't make stuff like that and there's a reason that police departments and self defense experts advocate the use of #1 or 00 buck. I like shooting stuff, though, and I hear people making claims about how they think wax slugs and other projectiles might perform. Rather than speculate, I'd like to have reasonably sound data.