Slide Fire is supposed to have a very nice bump fire accessory for hand held rifles, too.
I have a Hell Fire accessory for my Mini 14 but I haven't used it in years. It's sort of a curiosity. I used it once or twice...it does work...and then decided that it was kind of a quick way to go through ammo without much purpose. In other words, I really need some kind of a real life and death situation to justify going through thirty rounds in just a few seconds.