I never realised how many left eye dominant shooters there are. Nice to know we are not in the minority as i thaught. I am right handed, shoot pistol right hand, but rifles left hand. I guess it's like MikeyZ said, depends on what you are used to and how long you been doing it.
I shoot left handed and have no problem. I'm also left eye dominant. I haven't shot with a M4, but the AR-15 kept throwing spent shells onto my right cheek, hurt like ****.