I seem to recall that some of the bombs have the same sized casing; the amount of explosive is the variant.
Walt
Nope. Different size bombs have different quantities of explosive fillers. Most laser-guided bombs and JDAMs consist of guidance units and tail sections mounted on Mk-80 series "dumb" bombs, making them "smart" in the process. Net Explosive Weight (the actual explosive material in the bomb) is roughly 45% of the gross weight of these bombs.
Bomb weight (depends
on fin assembly)
Mk-81 260-305 lbs.
Mk-82 531-565 lbs.
Mk-83 985-1105 lbs.
Mk-84 1970 lbs.