1-2" at 100 yds is extremely optimistic. Most hunting rifles are in that category. 2-3" for sabot slugs would be excellent. That means that 150 yds would probably be the limit for me.
bswiv is right about the trajectory. The drop at that distance is going to be such that range determination will be critical. If you've practiced the shot at that range, and you know you can do it, then it's not unreasonable. If you can't determine the range with precision (like with a laser range-finder) then I wouldn't attempt it. I would also make out a range card that showed the correct hold for each 25 yd increment up to 100 and then each 10 yds past that. The card would be taped to the stock for quick reference.