Best I can come up with is to cut it at the end of the crimp and use a tubing expander tool, then weld it back together.
Or better yet, let me stick my arm inside of it and I'll do a single bicep curl. Done and done.
The thought process here is to let the water freeze and expand ~9%. Defrost, refill, and repeat.
Not trying to blow out the welds with high air pressure. I have access to pure nitrogen so if I go the heat route....
ExactWeld used to make beautiful expansion chambers. They cut out the two halves, welded them together and pumped them up hydraulically. But then again, the OEM's just stamp the two sides out and buzz them together.