That site shows the 10mm Cor-Bon 135 at 760 ft-lbs, if I'm reading it right (which I may not be lol).
I rechecked that, and you are right. I spent too many hours in a duck blind this weekend and I'm a little fuzzy. =)
Keep us posted on your .460 conversion if you go that way, I would be interested to see how that turns out.