When Warden Norton shoots himself towards the end of the movie,he puts the gun in the middle of his chin.After he shoots the wound is about 2 to 3 inches to the right.
Now, I don't have a lot of experience in suicide...really, who does? Anyway, from what I've heard, most people who kill themselves with a gun to the head in any way usually move at the last moment, usually missing. In "Shawshank", he didn't miss, but who's to say that he didn't flinch?
I know this is just "covering tracks", but it's such a wonderful movie and I'd like to keep up the illusion that it's perfect (or nearly so)