There are only 6 gun stores so far in Twilight City: Rupert's Gun Shop in Sobersville (10,10), Dougy's Gun Shop in Boltside (1,17), Eisenstein's Gun Shop in Winterville (25,11), Tyler's Gun Shop in Cider Hills (7,27), Cherry's Gun Shop in Capricorn Village (40,20), and Duane D's Gun Shop in Capricorn Village (32,29).
Gun shops are a good place to stock up on, you guessed it, guns! Below is a list of items found in gun shops and the percentage chance of finding them (percentage based on 100 searches):