NO NO NO,Installing a foregrip on any pistol is a violation of federal law unless you do a form 4.If you are talking about the folding stock rifle with a 16" barrel,it's ok. Steve
Correct. Installing a vertical foregrip on a pistol makes it fall under the Any Other Weapon (AOW) category and would require ATF registration.
http://www.atf.gov/firearms/041006-vert_grip.htm