The problem with rifled slugs is that they are specifically designed to not spin, and spinning them can indeed reduce accuracy in most types. The modern re-birth of the rifled choke is for sabots of course.

I personally prefer solid lead Fosbery-style projectiles, cast from a CBE mold or similar.

Pity the modern equivalents like the Dixie 'Terminator' are so hard to get hold of down here. Love to give them a try too.