4seventy,

I guess you are trying to pinpoint where the heat was applied on the lumps, as for example at the semi-circular section. It looked like the entire lumps were exposed, but I did not examine them closely enough to identify focal points. I am also not familiar with what exactly that guy wanted to accomplish there, so did not look further. What I kept in mind was that older guns might have been tinkered with. With 'Laufhaken' (barrel hook), we refer to the entire lump in German, by the way. 'Doppellaufhaken' would the be a 'double lump', I guess.