Ive got some weapon mods that fire by using right click. At point-blank range (interacting range), the npc's even if they are enemies, do not allow me to fire the weapon because when I right click it "interacts" with the npc instead of firing. I tried to disable everything that may cause this (lines, factions,..) and nothing worked.
1.7.10 did not have this issue. Played custom npc with flans and other gun mods and this never happened. I could even fire through friendly npcs.