I shoot .312 115gr. RNFP cast fairly soft in my 1902 M&P. I also shoot Hornady's .314 lead SWC in 32-20 and 32 S&W Long with loads in Unique, WW231/HP38, and Trail Boss.

Most commercial castings are on the hard end of the spectrum. The round was built around pure lead bullets, and our old revolvers were made to shoot that soft bullet. My S&W and my Colt haven't had any leading problems with .312 to .314 soft bullets at modest velocities.

I keep my carbine ammo loaded with jacketed bullets, and loaded to the higher velocity. That way I know all jacket ammo is for the rifle! Even thought ALL my ammo should be safe in the revolvers (made in 1902 and 1918) the Marlin is 80-90 years younger! BTW; regardless of when your S&W was shipped, all 32-20 S&W's were made before 1929, so the newest it could be is 89 years old. Just something to keep in mind, and parts are no longer available.

Ivan