hi,
you should always do some sort of color correction. I took the liberty of doing some adjustments to your image. I have no idea what kind of style your going for, so this is just a simple grade. Depending on what your trying to achieve in this shot, you could brighten the gun mans eyes, or highlight the gun more.
I think its best to try and get what you can on the day, and then clean it up in post. Don't ever be afraid of doing "post" work, its one of the most important aspects of film making......as far as im concerned :)
http://www.flickr.com/photos/38283616@N00/2752399937/
good luck