Jadnashua
Retired Defense Industry Engineer xxx
It takes a LOT of force to expand copper when it is not heated. If you took a section of pipe, capped each end after filling it with water (you'd need a plug on one end, as you wouldn't be able to solder a cap on after it was full of water, then froze it, it would expand. You might have to do that several times and the fittings may fracture as well as the pipe. The bursting pressure of 1/2" copper pipe is about 6000 psi for type M (the thinnest easily available). That's really hard to apply, especially evenly, without hydraulics.
