i think it also depends on your sesibility if u use wiimote and use the W@W scooping sesnsibility u at first have to hold breath but when you get used to it its no problem and with the MWR style you dont have to hold breath at all hope this is usefull to you

When I'm sniping (which is not too often) I tend to hold my breath for about a second right before I take the shot, to gain a bit of accuracy. I don't think you should hold your breath all the time, as it slows down movement and aiming.

Always hold your breath before taking the shot, this is necessary for a much more accurite shot. Do it a second before taking the shot, so hold your breath quick then fire. You're more likely to get the kill like that.

(Of course you can also hold your breath to steady your aim, but if you have steady hands like mine then you wouldn't need to hold your breath long)

Im a decent sniper imo, and thats because i use ACOG scope on my MSR. Im never good at hardscoping- so i use Marksman with my ACOG. I dont usually use the normal scope, but when i do trying to level up to get the ACOG scope, i hold my breath -till my soldier turns blue- cause im trying to line up the shot. I hold it for as long as possible, every time a kill comes my way.

For some reason I always hold breath when I ads with a sniper.  It might not be the best idea or the most successful, but i guess my reasoning for it is that when I ads at someone they are generally already in the center of my crosshairs so minimal adjustment is needed.  Holding breath probably isnt actually "needed" though unless the guy is far away.  Just my take on it.