Trigger device, fire when squeezed and released
I recently saw a video from the 2016 SHOT show which was profiling the new Fostech trigger assembly for the AR-15 which allows the rifle to fire when squeezing AND releasing the trigger. They have ATF approval for it.
That got me thinking back to the early to mid 1990's when I saw a Ruger 10/22 rifle which had a device mounted in the trigger guard which created the same function. It was thin blued steel and if I remember correctly, it followed the trigger guard up behind the trigger and had a small tang which wedged up behind the trigger. I am not sure of the mechanics of this but it did allow the gun to fire upon squeezing and releasing the trigger, effectively doubling the rate of fire.
This was pre Internet "e-commerce" days so it was likely mail order. I never saw it again and wondered if perhaps the ATF decided to regulate it. There were no springs, screws, adjusters or anything else, just a one piece thin steel device that snapped into the trigger guard and fit along the guard, wrapping up behind the trigger.
Has anyone else heard of this?