For those wanting to bodge in a hop up that works with minimal tools, and I mean absolutely minimal, here's a guide to how I do it using hot glue for the rubber. While the methodology is pretty crude, the results speak for themselves and there's not a whole lot that could go wrong.   First you get your barrel down to its bare essentials. In this case we have an HFC revolver's barrel and forcing cone. The way this is set up is that it already has a way to index the barrel so a lot of steps are