Go to the inner cities and get all the illegal firearms you want, if you have the cash for them. Those places are a fountain of stolen hardware and ammo.
Future jihadi attacks are going to be using the AR platform rifle. This strategy will result in restrictions of said rifles for use and purchase by US citizens. The result: targets for the jihadis will get progressively softer and easier. The continued use of guns instead of bombs will result in more and more restrictions for law abiding citizens. Once the guns are gone, it’s bombs away and more jihadi gunmen.