Exactly....how on earth did these things ever get approved is beyond me.
The technical details in the way the law is written is the answer.
Technically a "bump-stock" modification does not produce fully automatic function. All it does is
enhance normal semi-automatic action, which involves one shot per individual trigger operation, by
accelerating it.
Actually, were you to hold a semi-auto rifle in a manner which enabled you to pull the trigger as fast as you could you would come close to replicating the "bump-stock" effect -- which is not
automatic.
Back in the '70s I bought a device called a "Hellfire" which was advertised in the
Shotgun News and sold by a mail-order gun dealer in Waco, Texas (the
Branch Davidians). This device screw/clamp mounted on the rear of the trigger guard and behind the trigger of most
semi-auto .22 rifles. It was spring operated with an adjustable
finger that lightly contacted the back of the trigger. When the trigger was pulled, gently and with a relaxed finger, a single shot was fired and the devices
finger instantly pushed the trigger back to the initial position. So as long as the shooter's finger maintains the right amount of pressure on the trigger (which took a bit of practice) the effect is a rapid, harmonious action between the trigger finger and the device, producing an
accelerated semi-automatic function.
I installed this gadget on my beloved
Ruger 10/22 rifle, which uses a 50 round magazine. I ran almost two full bricks (about 1,000 rounds) of ammo playing around with it, which fouled the barrel and the receiver and got boring after awhile. The "bump-stock" used by the Las Vegas shooter is an elaborate, expensive version of the
"Hellfire" gadget. It replaces the existing butt-stock on the ordinary (semi-auto) AR-15 rifle. It has an
impact recovery slide built into it that produces the same, although much more mechanically efficient, type of effect on the rifle's trigger as did the
"Hellfire" gadget.
