I would add that a clean gun does not shoot the same as one that has a round or two through it. You want a fouling round or two before you really site as you are not shooting a perfectly clean gun in the field. If you are going to hit the field with a gun that hasn't been fired then you should go to the range and fire a 3 shot group just to get the gun fouled a little.
Tip from a friend of mine who was a long range shooter at NRA competitions.