Ok Ive managed this with a score of 37
Found these tips helped.
1. Turn your mouse sensativity down to about 1.8 from 3
2. Youve got 5 seconds for the shot take your time.
3. Wait untill you are positive your in the middle of a breath before you shoot. turn up you volume to be able to hear your breathing propperly. If you shoot at all while breathing you incur a accuracy penalty.
4. Keep your sights zoomed in all the time , just tilt down after every shot to aquire the next target.
5. Use CTRL to fire not left mouse,as pressing the left mouse can move the mouse enough to make you miss.
6. Change your gamma up and down with F10 and also your brightness with F11 . Do this untill the targets are most visable ,this helps to aquire them quickly and get to them fast.