Get an M40 with an Acog scope and have Steady Aim and Stopping Power. Taddaa....
Now watch this video by a really good no-scoper
If you don't learn anything from this, then get an MP5 with Stopping Power and stick with it
The actual tutorial starts at 5:30
[ame="
https://www.youtube.com/watch?v=DEoh3g1KqMk"]YouTube - zzirGrizz G-SHOT Tutorial[/ame]