TexasCHLforum.com

AOW Pistols

For pistols, there are a few situations where the weapon will be classified as an AOW....It’s also possible to use these mounts to attach vertical grips. If you do, you have created an AOW pistol and it will need to be registered as such.

Essentially, pistols are legally classified as weapons meant to be used in one hand (good technique calls for both hands, but, again, we’re talking about government rules). By adding an additional grip, you have made the handgun into a weapon that is now intended to be held with both hands, which would then classify the weapon as an AOW. So if you decide to mount a vertical grip, you would have to register the firearm as an AOW.