There’s video on my link as well. if the work well it could be a force mulitpler.
Slide-Fire and Bump-Fire are the 2 brands I’m familiar with, and they’re good. I was impressed with the AR-15 & AR-10 units. I already own Class III units on both, so it’s more of a novelty. I heard about early BATFE *problems* with them, but I guess that’s ‘worked-out”, now.