Sabot slugs are probably a better choice for rifled shotgun bores.

There are a LOT of different slugs to try, and you might spend lots of $$$ finding the best projectile for your barrel...

HOWEVER, foster type rifled slugs ARE a safe, viable, effective alternative for your rifled bore, and could be an accurate and relatively inexpensive choice, as your buddy has already discovered..

It wouldn't cost you much to find out.....

Good luck and keep us posted...