I came across documents describing quadratic and conical flash channels.
My first encounter was in French and German documents on 37x94R Hotchkiss cases and initially I thought this design has originated in France as Germany was a licence holder for the ammo.
But later I also found such flash channels being described for (DWM made?) 9.5mm Turkish Mauser cases dated 1887.
- What was the exact purpose of this shape (I suspect a venturi effect which created a faster/hotter flame jet)
- Who invented it? Was this ever patented?
Here a drawing from a German 1886 document.