Having had both a 12 and a 16 bore Simson, I am sure the 16 is a true 16 frame.

Between exterior of sideclips: 54mm
Between exterior of firing pins: 28.5mm
At widest part of action flats, at curve of standing breech: 40.5mm

Unfortunately no longer have the 12 bore ones to compare.



JC


"...it is always advisable to perceive clearly our ignorance."ť Charles Darwin