[Arran]

Russ;
  I have seen two ways of restuffing a plastic molded paper cap, bumblebee, black beauty, Little Chief, including yours, the other way was to cut one end off and bore out the innards, and then replace the cut end. I found out something interesting about the Sangamo "Little Chief" caps though, for years I thought that they were molded out of polyethylene or some similar plastic, but whilst cutting one open I found out that they are molded in something resembling either Bakelite or melamine as the produce a fine dust when you cut them. I crushed the shell of the same cap whist trying to clamp it in a vise and the pieces were all rough and jagged, just like a phenolic plastic. I think I may try the line boring method should I restuff them, since I do have a small lathe.
Regards
Arran