1) Bind 2 or more keys to hold breath (i.e. right mouse + m and/or n on your keyboard).
2) Use any scope on any weapon and press the three keys simultaneously.
3) Notice your scope isn't moving, so shooting, especially sniping, becomes much easier.
4) Test this twice after running and getting breathless. It still works.
5) Notice even the "white dot" stands still using this technique. So basically the key combination affects the whole "character-micromovement".