Use what you got.
So, if you have full choke try it.
If you have all three or four or five, try them as well.
I mean to say if you have in your collection the Rifled choke, use it that what it was designed for.
But, I would use at least a modified and go from there.
I have shot Federal Slugs out the Auto 5 I had a could smack a four inch paper plate out to 50 yrds, no problem and could lob 5 out of 5 at 100yrds not a four in plate mind you, but a big enough rock that I was havin fun making it turn to smaller rocks.
It is an experiment that should only take two or three boxes of slugs to determine what your gun likes.
But, if you have the rifled barrel try them sabots, but at 12.00 a box, I doubt you will be shooting rocks for fun.
Just my opine today.
Tight Groups,
Rob