So, I'm thinking...
Charging Minotaur shots increases accuracy and decreases that buckshot spread. Maybe even give a slight increase to push force.
I'm not sure how that will work with other ammo types, such as heavy rounds.
Unless every gun gets to charge a shot with stamina, Pairing charging shots with stamina doesn't seem too sensible. As I assume LeMoon was pointing out, stamina and charing shots seem to be completely different mechanics.