Sorry in advance for the long post. I have been working up some loads for a 300 ultra mag, with Nikon monarch 3.5-10x50 . I had been to the range with it several times and the last two time shot several 1 inch or better groups with a particular load. I had decided to keep this load so I load about 50 rounds and head to the range to get it sighted in. It should have only needed some minor adjustment. It is suddenly shooting several inches off from where it was the week before. I make the adjustments and get it close but it is still not grouping well at all. I go home clean it throughly and head back out yesterday. POI was about 2 inches high at 100 yards when I left the previous time out. Fouling shot is 3 inches high and 3 inches to the left. Let it cool and next shot is 2 inches high .5 inches to left. (I' m waiting several minutes in between shots). 3rd shot 3 inches hight and 3 inches to left. Adjust scope scope to move POI 1 inch right. Heres where it gets odd. 4th shot is perfect 2 inches high. 5th shot 7 inches high and good left to right. 8th shot is even with the bullseye but 6 inches left. Now I was letting the gun cool down well and I had my father shoot it as well and he was having the same problems. Scope mounts are tight. We are thinking it is the scope even though it is new. Any help or opinions would be great. Gotta get this figured out soon as we are heading to Colorado for elk in less than a month. Sorry for the long post.