• weight tape (the tape had him at about 640 lbs. Average)
• [girth x girth x length]/300+50 (this equation but him at 730 lbs. )
• various weight calculators around the web put him at 663, but I don't know the math they are using...
Ed: actually, I think those calculators are using this method:
Estimated Body Weight = Heartgirth x Heartgirth x Body Length / 330. (For yearlings divide by 301; for weanlings divide by 280)