I’ve noticed on several occasions now where Slim is firing inhumanly fast. HIs rifle is, so far as I know, the only semi-auto weapon which is not single shot. This means the firing speed is dependent on speed of clicks, which can be relatively easily manipulated with a mouse script.
TF2 had this same problem way back when, with the pistol used by various classes. You could empty the entire magazine in 1 second, creating stupidly high burst damage. I think that is what I’m seeing here. The solution is simply make it full-auto with a lower firing speed.