in my case I used a stainless steel rod that I had and took adhesive backed sand paper and wrapped it around the end of the rod so it just fit inside the carbon tube then do a whole lot of twisting, pushing, and turning to get it sanded out using long strokes. make sure you stop every now and then to check how far in the end of the liner with the ring will go into the carbon sleeve. don't make the mistake of using the muzzle end as it is choked and smaller diameter than the rest of the liner.