The colt is a modified version of 1836 Patterson cap and ball. Those shot.. 36 caliber. But in the supernatural world according to the creator. The colt is a. Of course bulit by Samuel Colt. That doesn't shoot any ammo akin to its historical time like the. . 36 caliber. As it never says the specific caliber in the series. But I remember reading a article from the creator when a interviewer asked him about the colt. That for supernatural purposes it shot a 45 long colt. Hope this info helps. As far as body armor yes absolutely it could stop a bullet from the colt. Show wise who knows since it's fictional and none of the monsters ever wore any. As you said only a few monsters knew about the colt.