I keep trying to find more info on the subject because I want one for my pistol. I cannot find anything concrete enough to give me piece of mind so far. There is the ATF reply letter that was posted here which certainly claims its ok.
I see lots of people now with pictures of AFGs on their pistols but lots of people still don't do it for fear. I found where someone posted a supposed official ATF article from its own website that was titled specifically for "Vertical Grips" Now if you ask me, the AFG is NOT a "Vertical grip"....if it was vertical, it would have been called the VFG and would be a 90 degree angle from the bore when mounted. I don't know that some radical person will try to claim that its vertical because its mounted to the bottom at 6 o'clock as opposed to a horizontal grip mounted at 3 or 9 o'clock
. I don't know who it is that decides what vertical grip even means.