I have a rifle that has been accurate in the past that seems to have developed a mechanical problem. I first suspected my scope so I swapped it out but still get the same shape pattern in my groups. I tried many different loads, different shooting rests and some are better than others but they all have this same shape in common. They form almost a diamond shape. Any suggestions? Here is an especially bad target that shows the shape and it was the target I shot before changing scopes. I have tightened up the action screws but did not take the rifle out of the stock or remove the one piece base from the rifle when I swapped out the scope. edge.