Posted by Marcus Merritt on February 17, 2014, 4:06 pm, in reply to "Pigeon grade question"
John: my 1905 12 gauge field grade has this firing pin feature. I believe it is to keep the firing pin bushing from rotating. The firing pin bushing does not screw in at a right angle to the face of the breach, it is at an angle so that the firing pin aligns properly with the hammer. Apparently, the face of the firing pin bushing has to be finished off flush with the face of the breach after it is installed. Hence the need for a set screw to keep it from rotating out of flush.