For most rifles and pistols, the answer is no. The National Firearms Act (NFA) restricts the purchase of ‘short-barreled rifles’, which includes any RIFLE that uses a barrel under 16-inches or fails to meet a 26-inches overall length. Very few AR-15s are sold as an SBR from factory, but if you are uncertain about a product you see online, check the product description. Most manufacturers will include a notice of its status as an NFA item. Please note, AR PISTOLS are exempt from the barrel length restriction, though pistols have their own limitations. You cannot put a stock on an AR pistol without converting it to an SBR, and if the pistol’s overall length is below 26-inches, you cannot use a vertical foregrip either. Whenever you’re making significant modifications to your AR15 rifle or pistol, make sure you’ve researched the law and feel confident in your changes.