I've killed a number of deer with my side by side rifled 12 bore shooting the 1 1/4 ounce Lightfield Slugs, which is what I regulated the gun with, when I built it. These are very accurate and kill like the Hammer of Thor. However, for big bears, I would recommend The Terminator hardened slugs, built in Tennessee, I think. Google up Terminator Slugs and I'm sure that you will find his site. Very knowledgeable, no BS guy too!