If your pipe is cool to the touch on the outside, it's more likely you aren't smoking it. Briar is chosen because it doesn't ignite as much as because it is an insulator. Certainly, a metal pipe would get way too hot to hold.
Interesting design!
Here's a Weber Streamliner that I restored for a friend a few years ago. He used it as a display piece, and I don't believe ever smoked it.