Your gunspec is in with your model in the guns file. The gunspec allows you to move the gun forward, backward, left, or right, but if you have the weapon backwards in the modeling program it will appear to be shooting you and then you simply just click on "flip handedness" or "right handed" to rotate the model. If you have fragmotion then it is easier to do these things without losing your animations. In your gunspec look for "alignz = 0" and put in whatever you like. I like to start at "15" and work my way forward or back. You can do this for the muzzleflash also. If you don't have a gunspec file, then I suggest one of eai's gunspec files, that way you don't have to worry about anything but the position of the weapon. Others may do this differently, but this is the way I do it, however imperfect it might be. Good luck.
