Some range lead might be good, but there will also be some that would not.
For smooth bore you might be safer, but there is still some chance that a really hard bullet alloy material deformed unnoticeably during casting could get stuck and further deform things in your barrel.
I do not know if that could really happen, but why take the chance?
I have used wheel weights for casting for both modern and BP arms from years ago, but no longer.
Now, I am even iffy about even running the older already various cast bullets that I melted and drossed years ago through my more modern cartridge rifles.
I am a little concerned that I might have possibly ruined an electric melting pot for making black powder rounds by having used these alloys.
I guess now I will dedicate this pot for modern cast bullets, and get another different pot to dedicate for casting muzzleloading projectiles.
Picking out recovered range lead might lead to getting even harder mixes of lead; who knows what people or manufacturers may have been casting in their projectiles, unless you have the box to identify manufactured projectiles and a lab to identify odd homecast alloys.
I would be concerned about ripping up rifling in any muzzleloading arms using unknown metals.
Another issue would be removing a stuck ball or canted conical made from a not completely known alloy.
Usually ,I can tell by how shiny it is after intially cleaning any crud upon the material. If it is shiny and reall hard, I will now leave it alone.
If it a duller color, dents easily in some pliers, and has a good streak on a cardboard surface, I might consider it for casting.
Also, if it shows some small amount of whitish oxidation (do not breath or ingest :nono: ), it might be also be a possibility for muzzleloading use after cleaning it up thouroughly and then must pass the three requirements I mentioned above.