mind you combat marksmanship doesn't require breathing, just the right position, and thats real life too not airsoft. Just going to put this out there, don't snipe, for more than one reason:
A: a real/good sniper rifle in airsoft is pricey
B: in the airsoft world its more like hunting then sniping
C: you like many others are not "born" snipers
D: its not cool like the video games.
E: you have to be pretty good to pull that ish off anyways.
i think most everyone could vouch for me on this, but i'm just trying to help you out since you seem pretty new to airsoft