Greenslade
I remember those brass firochi caps no 11 they took a good strong mainspring to get them to go and they were a very hot .I do remember one unhappy result with them ,a friend who was with me had a early Pedersoli sxs percussion which had a weak main spring on the left hand lock which did not fire the cap ,returning the hammer to half cock he remove the cap but the cap compound was imbedded on the nipple top and what he did gave us both a big shock to remove it from the nipple using his finger nail and off the gun went some thing I had never seen before or after
Feltwad
Maybe that was considered a "hang nail fire"!