Most shotgun hammers have a raised ridge across them, just behind the striker face & on top of the hammer.
I never have been able to find out what the purpose of this ridge is.
Is it a hang over from percussion cap hammers ?
Percussion hammers, however, enclose the cap so that pieces don't fly back into your face.
I thought this ridge may be to deflect upward any pierced primer gas that may escape past the striker.
Can anyone enlighten me please ?
O.M