An AR-15 pistol is a pistol-length AR-15 with no stock (only rifles have stocks). In place of a stock, an AR-15 pistol usually has a pistol buffer tube or similar piece that does not allow for the attachment of a traditional stock. To qualify as a pistol, there must be no vertical foregrip. An AR-15 pistol has a barrel shorter than 16 inches — this is the minimum legal length for a rifle barrel.
The National Firearms Act of 1934 (NFA) defines any rifle with a shoulder stock and barrel less than 16 inches in length and 26 inches in overall length to be a “short-barreled rifle” (SBR). It requires a citizen to fill out ATF Form 4 and pay a $200 NFA Tax Stamp. An AR-15 pistol allows the shooter to have the size, weight and maneuverability of an SBR but avoids the NFA regulations. An AR pistol is fired like a typical handgun. The barrel size is usually 7 inches or 10.5 inches, giving the shooter greater flexibility in close-quarters shooting. It is a great home-defense firearm for this reason. Due to its size, an AR pistol is easy to store and transport.