Sure it’s a detail in Batman v Superman fans have shown disapproval for on an ethical level, but it’s tough to deny how badass it is to see the Dark Knight wield some fire power. The Knightmare scene, as well as the other sequences which featured Batman with a gun, was accomplished between Ben Affleck and his stunt double Richard Cetrone– who expressed his excitement about breaking that taboo. In his words,
Article source: https://www.cinemablend.com/news/2551406/batman-stunt-man-explains-why-using-guns-in-batman-v-superman-was-a-lot-of-fun