Check out this article from the Washington Post:

http://www.washingtonpost.com/wp-srv/style/movies/features/gunfight.htm

It’s from 1998, but far from irrelevant. A sample:

Here are some of the things about guns that Hollywood doesn’t care about, and never gets right. First off, they are very loud. If you shoot them without ear protection, you deafen yourself. If you are surprised by their sound at close range, you flinch wretchedly. Your ears ring for hours or, as in my case, forever. Guns are also large, heavy and dirty. Carrying one, despite the immense evolution in holster technology, is no fun; it’s always slipping this way and that, it gives you a backache. A shoulder holster, so beloved in the movies, is really more like a brassiere with a brick in it. Most detectives take theirs off in the office. Guns wear out your clothes, either by abrasion or oil stain. They smell of oil. They go off accidentally far too often. (I’ve only seen one accidental shooting in movies, in “Pulp Fiction,” where Samuel L. Jackson accidentally shoots the guy in the back seat.)