I use 3 inch mag. "original" BRI (Ballistic Research Industries) 445 gr. 50 cal. sabot slugs. I bought them about twenty years ago when sabots were not so common. I used them in the southern tier New York state. I still have quite a few left and they are accurate but sadly are no longer made.
I used the 3" remington solid coppers till I ran out and My local shop only had 2 3/4"s. Gun is printing better groups and has a LOT less recoil. It still pounds You though. I won't go back to 3" slugs EVER!!!