they're advantageous to both - but finding a hunting sight that lets you do both isnt cheap.
2nd axis is just your level - making it right in the horizontal plane
3rd axis is your level also - setting it means you've got your sight aperture perpindicular to you.
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aka bucknasty
The average man seeks certainty in the eyes of the onlooker and calls that self-confidence. The warrior seeks impeccability in his own eyes and calls that humbleness.