Brass bands can be from 22-250 and 223, 25/06. Also .30 caliber casings can be use for a band alone. With the .22 cals the necked down part is a good transition piece from barrel to mouth piece. Also compression fittings work well for bands and transition pieces and can be chucked up in the lathe and turned down with carbide tools very easily to what ever shape you want. Turning brass I use my slowest speed and it works well for me. I have used deer antler, moose, elk, camel bone, acrylic, buffalo horn, warthog ivory hippo ivory and amber for bands and mouthpiece transition pieces. Pen blanks in those materials work well for those applications. Just throw some imagination in to the mix and you'll be fine.