I'm not certain of the material used nor the heat treat.. I am fairly certain these guns were proofed with shotgun pressure levels and would like to warn everyone once again that even if these shotguns stay together the headspace will grow rapidly as the steel deforms and/or batters and the locking systems are overstressed. . The difference in pressures is in the 25,000 - 27,000 psi range, even for the venerable 30-30. I you wish to do this sort of thing a thoroughly modern gun with modern steels should be used. Even then the firing pins will likely need replacing to handle the add pressure..and prevent primer extrusion.
