Not sure what sort of accuracy you are expecting but I doubt you will get any better than 3" to 4" groups at 50 yards from smoothbore using a hollow base slug. My good round ball groups run 3" to 4" at 50 yards and are better than any other home cast slug I have tried.
I have gotten some very good accuracy from several factory Foster slugs. I have also gotten some very good accuracy from home loaded Gualandi DGS slugs and AQ slugs. I have not been able to match the accuracy of those with any home made slugs I have tried to date.
Longbow