To be fair, the BMOL didn't have any bullets for the Colt and didn't know how to make any, so I can't blame them for not planning to use them to kill, well anything. They seem a bit like magpies, picking up every shiny (supernatural) weapon they can, whether or not they can use it. They had a lot in common with Ramiel and I hope they sent a reconnaissance team to his house, once he was dead, because that demon liked his weapons.