Might want to get input from others...
I would recommend Bismuth, as it - to me - replicates (similar) lead shot in patterning.
The 870 will handle this fine, it will just depend on your type of hunting, distances and patterning your gun to fit your needs.
Steve
Who last felled a honker with NEF Youth 20 ga with fixed modified choke bbl using 2 3/4" shell reloaded with #5 Bismuth.
Hey, I have done the pit blind, laying on back freezing my skinny rear off, field blind bit...and who knows what else for ducks, geese, critters in general.
Big wide ditch. I gots me a chair, already scouted how these honkers worked a field and with a wool army blanket I was sitting on, and around shoulders...
Hey if a dumb hunker is going to come up MY ditch, I can wait until ~ 20 yard until I see the honker's eyes go
and smoothly, but quickly mount my Youth 20 bore to face and slap trigger - still seated I might add.
*shrug* I sorta like this work smarter not harder stuff personally.
I mean y'all can get all muddy , freeze rear ends off and all if you want. I get landowner to drop me off at the ditch riding shotgun on a tractor.
Then again I too did the other stuff when younger...
I understand being older now why my Mentors & Elders did the stuff they did they way did it.
They sure shook head and grinned a lot too.
Got my honker, listened to the others making racket, landowner come back and I rode shotgun on the tractor with my honker hanging off the doo-hickey on the tractor.
Worked for me...