I just replaced the original pre-1936 "Perch Bellied" buttstock on my 1931 Field grade M12 20 gauge (28" mod. solid rib) with a later buttstock from a 1937 era M12 field grade 16 gauge- for my Grandson to use on clays-- I'll be dipped in batshit if you could "rotate" the receiver extension stud from TDC as it was set at the factory, to allow for this "cast" stuff- The rimmed radius on the face of the buttstock as it is mounted to the receiver boss doesn't allow for any of this "cast" stuff- and remember, factory specs. for M12's figure on the buttstock standing "proud" of the steel by aprox. 3/32"as per the Madis book on the "Perfect Repeater"--RWTF
