Take off the thread protector, then take a washer with a diameter larger than the barrel. Next push it against the back of the barrel snug against the threads and tape it there, I used painters tape however whatever you have to keep it from moving will work. Next get a new hacksaw blade and put it flush against the washer and start cutting using the washer as a guide. Once this is complete you'll want to file the end of the barrel getting rid of the cut marks and squaring everything up. Then take a brass screw and some valve polishing compound and use a drill to put a crown on it clean the barrel of any metal shavings and go shoot that bad boy. Mine was a 104ur for reference.