Forgive me because this is not really an AR, but I am trying to mount an AR compensator and other than possibly the barrel diameter the process should be identical. I have a Kel-Tec SU-16 5.56 rifle that looks like this: Notice how far the 18.5" barrel sticks out beyond the rest of the rifle when folded? I want this to be a backpack rifle and be as compact as possible when folded so I want to cut the barrel back and permanently mount a compensator so that the total length of the barrel and compensator is 16.1". The barrel diameter where I would cut it is .58". I know I need a crowning tool, but I also need something to remove material from the exterior of the barrel (make it thinner) so the comp will slide on. I already have the compensator I want to use, it is threaded for an AR. Since it is already threaded do I need to thread the barrel first and screw the compensator on and then pin and weld it? If not what tool can I use to remove the material from the exterior of the barrel? Is there a bit that I could use with a threading kit that just removes material but leaves no threads? Not really sure how to proceed. Any advice is greatly appreciated!