Plasma spray welding is a low temperature build up process- the heat input into the metal is low, prevents distortion-- most hinge pins are a free machining grade of steel in US made weapons- AISI 1018- and then oil hardened to a Rockwell C scale in the 56-62 range--As your shotgun was made in Germany, the steel will most likely be Krupp or Siemens "Hardstahl" with a higher nickel and chromium content- the Germans and Austrians built their firearms to last for centuries to come- and their metallurgy is unsurpassed- IMO-- But heat input from the TIG (tungsten inert gas) process is difficult to control on a radiused area- and the heat 'chases itself in a manner similar to a Mobius strip configuration- Plasma does not allow this to happen- I would suggest Kirk Merrington in Kerrville, TX. You are indeed fortunate to have such a fine "schrottenflinte"- the Spanish guns for years suffered from an ill-deserved reputation as having poor metallurgy- guess "Cactus JacK" O'Connor forgot about the great swords made in Toledo, Spain- no es verdad???
