I think that the game should be able to fit the 12 gauge ammo into the flaregun. In real life flareguns are 12 gauge and should be able to fit the ammo. In WWII they used to be made out of metal and could be used as a handgun. They decided to change the design strictly to hard PVC plastic for obivious reasons. All though being plastic, it does not explode - all though there is always a chance percentage that it might. That shouldnt stop the game from being able to use this to its advantage. There is a new level of trust/distrust between someone who runs up onto a person holding a flaregun. There is a chance its just loaded with a flare, but if not, its 12 gauge ammo. it should be ruined after only a few shots. It may also backfire on the user, not only are the bandits not to be trusted, now the weapons can even turn on you. see video
<---- 12 guage plastic flaregun shotgun ammo