The firearm must be registered because such a firearm constitutes “any other weapon” (AOW) as defined in the NFA at 26 U.S.C. § 5845(e). To lawfully add a vertical fore grip to a handgun, a person must submit an ATF Form 1, Application to Make and Register a Firearm along with a fingerprint card bearing the applicant’s fingerprints, a photograph, and $200.00 making tax. An applicant’s ATF Form 1 will be approved if the applicant is not prohibited from possessing a firearm under Federal, State, or local law, and the applicant’s possession of AOW is not prohibited in the applicant’s State of residence. An applicant may only add a vertical fore grip to the handgun designated on his/her Form 1 only after the applicant’s Form 1 is approved by ATF.
[26 U.S.C. § 5845(e)]