Here's a picture of the repaired crown on a 1939 Mauser barrel. This barrel has been in the family since about 1956. The repair was obviously done professionally.... the work is excellent, IMO. Note the silver solder that I believe was used to fill a void caused by damage to the crown area.
I once owned a 1918 - 1920 Luger that had a firing pin that had been repaired using silver solder. The repair was quite nicely done.