I know putting a vert grip on a pistol makes it a AOW and need a stamp, and a stock on a pistol makes it a SBR. Would attaching a handgun to a tac rail on another handgun change its legality? Im not referring to a AR pistol or a AK pistol. Im generally curious.
If you attached a semi auto to a tac rail (not exactly an easy task, in the first place. Top of one pistol to the bottom of another) the bottom pistol is not likely to function, unless it's attached by it's frame.
You would have an easier time attaching a revolver.
Unless you are pulling the trigger on both, at the same time, I would think that the BATF could/would veiw it as a grip. It would be "redesigned" to allow two hand grips on the original pistol.
Now, I am by no means a lawyer or an ATF agent but I have never seen anyone try it up to this point.
I seem to remember a super small, blocky looking .22 semi-auto that would attach to the picatinny rail on the bottom of an AR forearm.
I want to say they called it a "zip-gun" but then that doesn't sound right.