Ive heard that if an AR pistol is larger than 26in overall a vertical foregrip can be added without NFA paperwork. It is just classified as a "firearm". I also know that if a zip 22 is added to an AR pistol it is an AOW because its considered a vertical foregrip. So if a zip 22 is added to an AR pistol over 26in overall does it require NFA paperwork? I dont own a zip 22 or an AR pistol, but was just thinking about this and want other opinions on this.