I would say that you really can't base too much analysis on just three shots. I plotted the hits as you've described, and what you had (correct me if I'm wrong) was two shots very close about 1" above the bull, with one about 2" L, 2.5" H from the bull. Or, in other words, about 2.75" left and 1" higher than the center of the closer two shots. It the wind was gusty, I'd say that the chances are good that you just fired right as the a wind gust came up. Blowing a low BC ML bullet 2.5" off course at 100 yards is not that hard for a 15mph wind to do. Either that or it could just be a flyer. They happen sometimes for reasons that only God knows. There are a dozen things with ML's that might cause a flyer that's a total of about 3" out of the group. You already said you were in a hurry, after all.

My recommendation would be to go back to the range on a calm day (early AM is usually best) when you have ample time, so you can go slow and concentrate on every aspect of loading and shooting and can put more than 3 rounds down range. Don't change anything yet. Shoot another 5 shot group without changing anything. THEN judge the group. Chances are you've just got a flyer. If the group is showing obvious left-right stringing (not just a big group centered around a point) that didn't exist with open sights, then the first thing I'd check is the scope mounts. Make sure the screws are tight. If they are loose, you might want to remount the scope and use a dab of Loc-Tite Blue on each screw.

Mike