I take a ball end dremel cutter that is about 1/4" diameter, and make a groove on the end of the muffler. A barb would be better. I have to file a bit to get right in close , and make a neat job. The tie wrap is not grabbing on a positive taper that way. On some mufflers, I have turned the barb on a lathe, but most tailpieces don't allow this because of the shape. Some guys drill and tap for a small round head screw and it keeps the tubing from slipping off.