What problem are you having Chambering? How do you hold the reamer? Watch some Utube videos. That's how I learned to do it. Tried to do my first one using the drill chuck in the tailstock and wound up with an oversized chamber. I knew I had the tailstock lined up straight with the headstock. I used a dead center in the tailstock and it worked perfectly.
Used a floating reamer holder in a drill chuck in the tailstock. Turned very slow and used plenty of Vipers Venom.