(a) Firstly, set up the chamber end of the barrel in a 4-jaw chuck with protective padding and using a dial test indicator adjust the jaws until the barrel runs true.
(b) As a double check, look in the head stock end of the lathe and visually inspect that the chamber and barrel are running concentrically. You may notice that the muzzle end of the barrel in not inline with the centre by as much as ˝ an inch. It is important to ensure that your chuck jaws are tight and pull the barrel to line up with the centre. When you turn the lathe on the barrel may look as though it is running like a banana. If you do not feel confident to continue, recheck (a) and (b).