Even at close range bird shot is not effective enough to ensure it is a fight stopper.

Will it ruin someone's day? Yes. But it may not take them out of the fight. You don't get to chose when the fight ends, only the attacker does, either by turning and running or by becoming noneffective to fight through blood loss or CNS disruption.

There are 3 basic responses to a threat, fight, flight or freeze. If you turn the tables on the attacker he is likely to do one of those three things. One is still press his attack. Having sprayed him down with bird shot may not have done anything besides made him attack more.

Wax slugs with bird shot are cute, in the same way Glaser Safety Slugs are cute. The idea is nice, but the terminal effect on a motivated, aggressive target may not be optimal.

While calibrated ballistic gelatine is useful for information gathering and some data can be correlated it is different from actually shooting someone with it.

KBK