The ATF legal Bumpfire AR stock

Slide Fire Solutions has developed a stock for the AR-15 that facilitates bumpfire shooting. It is reminicint of the ill fated Akins Accelerator that was initially approved by the BATFE but later deemed a full-auto device and banned.

I am not sure quite how this works, but the BATFE approval letter and the Slide Fire website indicate that there are no mechanical parts. It seems to be using the buffer spring to provide the forward "bumping" force. This is unlike the Akins Accelerator which had its own spring system. The lack of any mechanical parts may be why the BATFE approved it.

Video and more info............ here
Say Uncle has a discussion going......... here