As Axxe said, best to have a gunsmith or machine shop experienced in firearms work remove the barrel and thread in a lathe. That being said, I have sucessfully threaded an AKM, AR and a Mini-14 by using a bore guide purchased from Brownell's to make sure the threading die starts square to the muzzle. My decision to do the job myself was not based on the cost but due to not being able to get a shop to get around to it for several months. If you can get a shop to thread your barrel without having to wait till your hair turns grey, that would be the preferred method. If your hair is already grey, then there's no hurry !