I agree, big slugs have their problems, but lethality is not one. The "boiler room" on a deer is a good 16" across on a mature deer in MN, but with big shoulder bones, and ribs, small bullets can deflect if its not threaded in behind the shoulder. A shotgun slug, regardless, will punch through anything on a deer. They are not much tougher than a person, and the military uses the tiny 5.56 to good effect.