According to the L C Smith plans & specifications book frames were made from 1020 steel. They were made from a forging. 1020 is a carburizing grade of mild steel, & is in no way at all related to cast iron. Most shotgun actions are not suitable for high pressure rifle rounds. Most, including the L C Smith, should be up to black powder levels of .45-70, .38-55 etc. Large dia firing pins should never be used for high pressure rounds.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra