You might want to consider silver soldering. The entire liner does not need to be soldered, just one end. For a short distance. Don't use anything from Brownell's; get the real thing from your local welding supply. True silver solder is expensive but also low temp and uses special flux. The metal never even darkens.
I've used stippling, threading, and heat shrinking/freezing on the P1 barrel liners. Pinning turned out the most feasible.
I never bothered with trying to re-line Luger barrels. Why bother when you can buy brand new barrels completely machined??? Collectors don't want re-lined Lugers. There's just no profit in it.
