I gave the LCSmith 20ga SxS that belonged to my mother to my 12yo grandson. He wants to take it duck hunting. Im not up to date on non-lead shot. Is there any lead free shot that would be safe to use in this 70+ year old shotgun? thanks for the help!

Bismuth is your huckleberry.

https://bossshotshells.com/

Yes bismuth is the way to go. I shoot old hammer sxs's for waterfowl, 12 and 16 but with 7/8 oz of bismuth 5s. I do load my own but there are a couple of commercial loads out there.