Yeah, that JHP ammo can smart real good if you're unarmored. Desert Eagles are even worse. The Toughness perk can be a lifesaver, and armor is necessary. All the shotguns do have a +20% chance to hit, to represent their spread (try comparing your hit chances with a Shotgun and a .44 Magnum which has the same range, and you'll see). It's hard to tell what AC really means, but in the end I decided to give -AC only to ammo that pierces armor, explodes or burns, and the Shotgun shells don't really fit into those categories.