RE: Leveling crosshairs
I know what you mean. What looks level inside may look askew outside. One of the cheapest ways is put up a large target with zeroing squares, and set the vertical axis by putting a lead sinker on the end of the string. Then you will be adjusted to gravity. There are fancier ways and equipment to do this, if you want to buy it. It would concern me if I did really long shots, eg, if I planned to hunt in Montana or Idaho.