Seaoat,
Barney never fired his gun once the whole time he lived in Mayberry.
In fact, I don't think anyone ever fired a gun in Mayberry.
The closest thing to gun violence in Mayberry was the time Gomer was stationed on the roof of the courthouse with a rifle because bank robbers were known to be coming to Mayberry from the big city (somewhere up north cause they had yankee accents). But Gomer fell asleep up there holding the rifle.
When Barney startled Gomer, he rose up and dropped the rifle off the roof and onto the street below. But the rifle didn't go off.
The yankee bank robbers were apprehended however. Except when Andy and Barney put them in the cell, the key to the cell was hanging on a hook beside the cell door and within easy reach of the jailed robbers. That was so Otis the drunk could let himself out of the cell once he sobered up.
But luckily, being yankees, the bank robbers were too stupid to see the key in front of their noses.