Since it's in the news, and since they're not capable of facts, I thought I'd provide some.
There are videos on youtube, btw.
At one point, someone tried to springload a stock to increase rate of fire. ┬áATF ruled (correctly, given the law we have, which I disagree with the existence of), that it became a recoil operated machine gun.
So, the spring was removed, and some redesign made.
The stock slides on the rear extension of the rifle, back and forth.
You push the weapon forward with your off hand, and pull the trigger with the right. ┬áThe recoil slides the gun backward, and the trigger goes inside the stock, disengaging.
Then, when recoil energy diminishes, the pressure of your off hand moves the weapon back forward, the trigger emerges from its shroud, and your finger activates it again.
Because it requires constant repeat physical effort, just as a Gatling gun would, it's a manual trigger. It requires a separate motion for each shot, unlike holding down a trigger.
It does require practice to use without failing, or even jamming.
The weapon is in constant motion apart from its own mechanical cycle, which just destroys any accuracy you might have.
So, when all is said and done, you waste ammo with less accuracy than actual full auto.
"How would it be different if he hadn't had one?"
In reality, he might actually have killed MORE people if he had to aim.
There's some alleged veteran's group of socialists on Fecesbook who claims this gimmick turns an AR into and M249.
No, it does not turn a closed bolt self-loading rifle into a belt fed, open bolt support weapon. ┬áThat's just complete bullshit.
But then, socialists have never been capable of honesty or integrity, and should be ignored.
Pinochet did nothing wrong.