So I had some cases I needed emptied so I took a buddy out to to shoot steel and water jugs at 500 yards. He has never tried to honestly hit anything past 100 so I figured he would have a good time. We get set up at a new spot and range the target at 487. Shooter told me 7.6 minutes so I dialed 7.5 and for a 6mph quartering wind. First shot hit about 1" low of center on a 10"x10" plate.....perfect. I send another round and hit the plate right on the lower edge......ok I yanked it. Third and fourth shots were just under the plate.....WTF! I dial up 1 minute and am back in the middle of the plate. It stayed there and we continued to shoot and bust steel and water bottles. This is a proven load and have shot it to 775 yards. The rifle recently made a trip to Northern NM and was subject to sub zero temps. I never had a chance to shoot it up there so im not sure of how it would have performed. I did a velocity calibration and it showed a loss of 140 fps. I am not too concerned right now because I don't plan on shooting these loads again. I needed to empty some cases for new load developmet. I just dont understand what happened. I double checked all the data in Shooter and checked the atmospheric inputs that Shooter input against my Kestrel (station pressure) and everything was good. Ideas???????? The load was 260 Remington 42.5gr H4350 120gr TTSX 2900 fps.