>Once they have a registration for the firearm, they are allowed to purchase or be in possession of ammunition, but only ammunition of the same gauge and caliber as their registered firearm. For example, a person with a valid registration for a 12 gauge shotgun cannot be in possession of or purchase nine-millimeter ammunition that goes to a pistol. The type of ammunition someone purchases must correspond to the firearm that is registered in DC to that person. https://washingtondccriminallawyer.net/dc-gun-lawyer/ammunition/laws/