They are not hard to make. You can make one, thread the barrel, and be testfiring it in half a day. You do have to pay the ATF a $200 tax, and get fingerprinted, tho. Getting the approval takes many months, too. A good one is 1" in OD, by 6" long, and needs a solvent soak and air nozzle blowing out every 300 rds or so.