I used brass tubing from the local "hobby" store. This tubing is already annealed and has a .015" wall. Each successive tube size is a sliding fit into the next larger size. The pieces are about 12" long, iirc. That was a long time ago. The tubing is in a rack on a counter top or shelf & runs up to about 1" in diameter.
I have also used it for making powder measures for my BP guns, shoving a piece of wood into one end with a cross pin then cutting to whatever length I needed, from measures only .030" OD holding 20gr. pdr. up to 5/8" & holding 125gr., 140gr. and 165gr. for the 14 bore rifle.