Well...
Somewhere, I have a copy of a Dale Storey(sp) book on shooting muzzleloading rifles and he performs an interesting test.
He takes a length of copper pipe(for plumbing - not sure if it was regular water pipe or the heavier ga. for heating)
He places the end in an empty soup can and fills it with molten lead to hold it in place.
He drilled a flash hole and used cannon fuse. It must have been 5/8 or so because he loaded it with a reasonable charge (80gr+) of BP and either a 54cal conical or PRB,
Boom.
Fired perfectly w/o any measurable changes in the pipe. IIRC he did this a few times.
I think that he was pretty surprised.
I am not recommending anything as thats why we have barrelmakers. Spending the extra money on a blank certainly beats the big "?" of just how many firing cycles that barrel will last before it doesn't. Just interresting to see how some metals handle stress.

Tom