Here is the point and exact reasoning as to why you should use the local patrol officer's weapons and ammo exactly.
Sorry but you take a valid idea and stretch it too far.
So have you had the same training as the LEOs?
Have you had your proficiency documented regularly?
Does the city buy you your gun and ammo?
I don't think so.
You are in a different situation. While I would advise against any round advertised as a "Man Killer 3000" and using a Desert Eagle .50 with "FINAL JUSTICE" engraved on the side there is no reason to shy away from a legal standpoint from any commonly available ammunition type in general use or caliber functionally suited to the task.
Fish was hung out to dry on caliber and bullet type because his representation was stupid.