Could be any of these listed ^^^. Sometimes heat can be the culprit. Use bags, coats, or sled to get the most stable shots. I seen a guy at the range with a no touch lead sled with a bulb to squeeze to the trigger. Thought this is possibly one of the best setups, but I just use bags or anything to get a solid rest. I was using some 180 grain blue box and thought I had my rifle on zero. My grouping starting getting eratic the more I shot. I decided to rest on every shot until the gun cooled down to shoot again. Next shot was dead center of the bullseye. Some guns have a suggested ammo and just like certain ones. I try to buy at least two boxes of the same ammo. That way if something seems to be off with the ammo I will know. I will say it again, I hear some folks say certain guns can like certain ammo too. I can say I have seen that to be true. Always try to shoot some freehanded if you are sitting in an area deer can sneak up on you. Sometimes the deer don't know they shouldn't come from any direction. It is better to be more prepared than not.