10 Ga
Go with the Lyman slugs, they can be loaded in a regular shotshell loader and for me have been very accurate in three guns including my sons NEF Tracker 2. I used to roll crimp slugs and it is a PITA, you need a fixture to hold the cases and a drill press to do a reasonable job. When I load the Lymans I dip the petals of the shotcups in powdered graphite, they seem to load easier and shoot a bit better, I get 3" groups with them using Blue Dot loads from the Lyman manual. We've taken 4 or 5 deer with these from 10 to about 125 yards, all one shot kills, none ran more than 20 yards or so. I cast mine from wheel weights for the penetration. As others have noted they do not lead the bore.
Best