What do the ends of the copper pipe look like ?
What diameter pipe?
Do you think you could just pour in #9 lead shot (used in shotshells) as weight verses melting it all? Or may be use some steel shot to make the lure act like a big rattle chamber? Once you crimp the ends you could solder it so the stuff doesn't leak out.
I have some old shot laying around and should try it out.
Threaded Mode