Ok, heres a longshot. What about a section of a fishing rod. There is a nice taper and the end could be plugged and drilled to the correct inside dia..If need be. I think almost all fishing rods have a gentle taper and a broken fishing rod should yield several barrels if you know what I mean..Also would be a tremendous wieght savings as compared to a machined aluminum one.Hope this helps you to consider alternatives.Check out the rods at your local sporting goods store.
Greg"Detailfreak"Rowley