Red Elderberry has a natural pith about 5/16" all along it's length. I drilled out this piece with just a sharpened piece of 5/16" dowel all the way through, then sanded out the bore true with two 5/16" wood dowel mandrils. 150 and 220 grit sand paper glued along each mandril. The bore was then burnished with a piece of 3/8 poplar dowel.
I made a plug with some oak dowel and glued it in with birch bark tar about an inch into the bottom of cylinder.I left an inch sticking out so I could chuck the cylinder up in my spring pole lathe. One problem I found was that the pith had a slight taper. I had to sand out the bottom half of the cylinder to remove most of the taper.
Would have been easier to drill out pith first before sanding out to eliminate bore taper. My next one will be drilled with a stone drill and trued with sand and rock dust
placed into the bore along with mandrill and cylinder spun with pole lathe. Once bore is trued I'll burnish with wood mandril, then glue plug into bottom of cylinder.
Anyway elderberry works great without a brass liner, and my birch bark tar glued plug is holding fine. Pine pitch glue would also work. Drilling all the way through
cylinder has some advantages. You can hold cylinder up to a bright light and check bore. After burnishing the bore should be shinny one end to the other. After turning
on my lathe and sanding I stained and rubbed with bee's wax. The cut through rings make the cylinder look like bamboo. I used an o-ring to test out cylinder [it lit first time] then removed and wrapped sewing thread around piston groove. here's pics cheers fiddler49