Imagine what would happen if an American tried to write about ale or brewing a cup of tea
I'm from the wilds of Oregon. The gun racks in the backs of pickups aren't just a fashion statement. A lot of people hunt, which saves the State the cost of hiring rangers to cull the growing herds of deer and elk. That sort of knowledge is a little more common than in New York City where guns are effectively illegal.
As I said, if he needs a few unusual horrors there's always the "exotic" shotgun ammunition. Not suitable for hunting. Very difficult to explain to Officer Friendly why you used them for self defense. But there for the true enthusiast, the specialist and those attempting to compensate for physical inadequacies real or imagined.
Here's a test of some of them
http://www.youtube.com/watch?v=paPJqUA86jwAnd here's a catalog with pictures
http://www.deltaforce.com/catalog/12gaugeammo.html . The turn your shotgun into a flamethrower and foul the barrel Dragon's Breath isn't there.