I want to know if the different shotguns have differing amounts of damage they do (and if they vary at range). I also would like to know if the different ammo types cause relatively different damage levels for different shot guns. For example, does a USAS slug round cause less/more damage than a DAO slug round? Also, if there are differences, has anyone actually quantified those differences? Does anyone have information on this?
The shotgun only determines the accuracy, rate of fire, recoil, bullet drop, bullet velocity, etc., i.e. they determine how a round is fired. Damage is entirely based on the type of round being fired. This is true for all guns in BF3.
Like most games with range factoring in to the damage equation, rounds do maximum damage within a certain range, and then damage decreases linearly until a certain point, after which damage will be the minimum amount.
Frag rounds (semi-auto): 20 damage within 8 meters, 10 at or past 40 meters
Frag rounds (pump action): 60 damage within 8 meters, 10 at or past 40 meters
Additionally, frag rounds to 30 explosive splash damage within 1.5 meters, decreasing linearly to 0 at 3 meters.
Slug rounds (semi-auto): 50 damage within 8 meters, 34 at or past 40 meters
Slug rounds (pump action): 100 damage within 8 meters, 34 at or past 40 meters
Buckshot rounds: 20 damage within 4 meters, 6 at or past 25 meters
Flechette: 14.3 damage within 12 meters, 8.4 at or past 25 meters
Stats are from http://symthic.com/?s=bf3&sb=dmgchart, and may change in future updates.