I'm speculating here but it seems like if the plane were to be used as a weapon, and I'm not saying it is going to be; the best method for maximum destruction would be to take the airplane to as high an elevation as possible and then point it straight down or at an angle.
The maximum take off weight is 545,000 lbs.
Subtract the empty operating weight of 297,000 lbs.
31,000 gallons of fuel weigh 210,800 lbs.
A fully fueled Boeing 777 can lift 38,900 lbs. (military press or bench?)
So 19.45 tons of what ever, 6,000 miles.