Short Barrel rifles have a barrel length of less than 16".  This is a class 3 item and we have many for sale.  You can buy one of these guns in most states, but they must go through a licensed dealer that can deal in NFA firearms.  We have many of these dealers on file, and you can pick one near you to help you with the transfer.   A transfer will take a number of months to complete, and requires that you can through a federal background check, and get the signature of the chief law enforcement office in your area (city Chief or county Sheriff- in most cases not a problem).   We process many of these each year and can help you through the process.