Interesting. I am M-16 armorer qualified, but I admit to being unfamiliar with the device of which you speak. Can you provide details and/or links please?
They're adaptations for semiauto AR15s, using parts from the M16A1 in the case of the auto-sear, but not the lightning link. Though mostly encountered in and around law enforcement circles, I've run across them in military use in Mexico and El Salvador.
Auto-sear background and timing info *here.*