I'm a 40 year member of the Plumber's Union

1. Water pipe is for water, not gunpowder!

2. If the copper pipe mentioned by Tom H was ACR (air conditioning, refrig.) or Type L it probably could stand a blast or two. However, pieces of copper pipe are very hard to dig out of your eye.

The water pipe isn't a problem with pieces in your eye, as they will penetrate a 2x4 stud quite easily. Just be sure to mention exactly what type of flowers you want.

If either type of metal was a viable alternative for gun barrel material, there'd be a lot of copper guns.

Yes, I know - brass cannon. Iron cannon - A hell of a lot of iron and brass turned from barrels to missiles during the fabrication of cannon from 1546 to 1900.

Yup, pipe bomb. Lots of them made with FFFg.

Plus, I've heard that a protest group in the USA - BATFE - takes a dim view of unregistered DDs. $25k and 5-10 years. Imagine there's a like group within 30km of your billybong.

Your call.

Is your widow - ahh, err, WIFE - pretty?

...and yes, you are a candidate for the local Australian Darwin Awards.