Barrel tightnening?
 

I recently purchased a number of guns from a shop that will be closing. All of the firearms were in need of some repair. In the group there were 4 Lugers and magazines. Two of the pistols look mostly complete and matching. The other two are mismatched and missing some parts.

One of the pistols, a 1917 ERFURT, has a barrel that is loose. I can remove the barrel by hand. If I tighten the barrel it will stop on time, if it is tightened anymore it will over time. Is there anyway to fix this? Peening or shimming? The barrel looks in fair to good condition.

I have removed and installed numerous rifle barrels, but Lugers are new to me.

Peening the flange or a shim- as you say.
A shim that thin will be a bear to make, you will likely need a surface grinder and magnetic table.

With either method, I would add loctite to the threads on final assembly; after confirming headspace is in spec.

If this is not one of the matching pistols, you may want to consider a different barrel, that one does not have the greatest bore anyway; of course that would mean having several barrels to choose from for fit.

Lugerdoc or GT could help you with a different barrel.

Thanks. From initial observation it appears to be all matching. Even though the bore is not in the best of condition, it would be nice to keep the original barrel if it can be fixed properly.

Something thin to take up space might also a be a bead of silver solder, or one laid down by micro-welding. Unless I'm mistaken, peening can squish again. And I agree that making a shim that thin would be next to impossible. Extending or adhering something permanently to the bearing surface of the flange, then facing it off on a lathe until it's just right would be my first choice. Loc-Tite might also do the job by itself if it clocks close enough. I've heard that 1/8 turn with the wrench setup after the hand tightening bottoms out is about right. If the barrel will hand tighten beyond proper position, though, I'd nix the Loc-Tite only approach.

how to do it?
 

Hi David, you're mostly right, but the correct repair doesn't involve any type of welding, or heating, etc.
What one does is cut a .020" shim, which is thick enough to stand the finishing torque and restore the correct indexing, (1/8" as you describe is about perfect). Then you cut the barrel flange back approx. .010" or so and then assemble with the shim in the normal way... best to all, til….lat'r....GT.....;)