Aw, geez, I wish he hadn't done that.

What's the problem? Glock is famous for making pistols without external safety latches. That's the problem. (You can have a manual safety installed on a Glock, but if your character is using one of those, you had better explain it.)

Readers like me, and there are many, are distracted by such errors. We lose confidence in the writers. The mistakes jar us out of our focus on the story and turn attention to the writing. In fiction, the errors usually aren't fatal -- we go on reading, but with diminished enjoyment. In nonfiction, mistakes about firearms can be deadly to a writer's credibility.

Firearms mistakes are common in all forms of writing -- news stories, TV and movie scripts, opinion pieces, novels. So common, in fact, that it is more surprising than not to read a story about firearms without catching the writer in a mistake. The subject is confusing for many writers, especially those who haven't handled guns or shot them. But writers who want to earn and keep the trust of their readers, not to mention their editors, need to avoid mistakes.

I will give you some tips on how to do that, but first, let's look at some of the most common mistakes to guard against:

• Confusing terminology. "Cartridges" and "bullets" aren't interchangeable terms. A bullet is one component of a cartridge, the one that flies from the gun muzzle. "Spent bullets" and "spent cases" are different things. Which did the police actually find at the crime scene? A spent bullet is one that has stopped moving after being fired. A spent case is one from which the bullet has been fired. Either might be found at a crime scene, but spent cases are more likely to be lying in plain sight.
  
  
• Confusing types of guns. Rifles and shotguns are different. The terms aren't synonymous. Revolvers are different from semiautomatic pistols. The term "automatic revolver" is almost always an error (there is an obscure exception but you are unlikely to encounter it outside the specialized firearms press).
  
  
• Getting technical details wrong. Does the gun have a safety or doesn't it? Many revolvers and some semiautos don't (because their mechanisms make them unnecessary). Your character can't "check the clip" in his revolver, because revolvers don't have "clips" (or, more properly, detachable magazines). If the police report said the suspect had a .380-caliber pistol, don't assume it is a typo just because you never heard of a .380. Chances are it was a .380, not a .38. Reporters, by the way, are notorious for writing caliber designations improperly, putting periods in front of metric numbers. They write ".9 mm," producing an absurdity, since a bullet that small would be less than a millimeter in diameter. "Assault rifle" has a specific meaning -- a fully automatic rifle, not a semiautomatic rifle or a rifle that looks menacing or militaristic.
  
  
• Using loaded language. I mentioned "assault rifle." Not only is the term often wrong, besides being an obvious redundancy, but also it is loaded. The phrase implies that a rifle so labeled is more sinister or more deadly than other kinds. Nonsense. All rifles can be lethal, but in fact many deer rifles use cartridges with more range and power than the military's infantry weapons. "Arsenal" is a commonly misused word that is also loaded. Again, it implies menace where there may be none. Many people have gun collections that are perfectly legal. (One reporter wrote that the police had seized "a small arsenal of four guns.") Other loaded terms to watch for: "Saturday Night Special" (vague, but also racially tinged), "weapon of mass destruction" (ridiculous description of a sawed-off shotgun), "cop-killer bullets" (a highly charged description of a bullet that doesn't exist).
  
  
• Using stereotypes. In fiction, stereotypes are too shallow, too cheap and too easy -- they are crutches for hacks. In nonfiction, stereotyping people is unfair and misleading. The truth: Only a tiny minority of people who own guns use them for crimes or otherwise cause harm. Only a small minority fit such stereotypes as beer-swilling rednecks waving guns or incompetent boobs who shoot themselves or their friends.

Writers owe it to their readers and to themselves to be accurate and fair. But how do they thread through the thicket of misconceptions, misinformation and sheer arcana, some of which is counterintuitive? For example, the uninitiated might logically assume that a shotgun shell with No. 8 shot would be more powerful than one containing No. 4 shot. The opposite is true. To avoid errors (and embarrassment), you will need to do some research. You will need to learn at least a little about how firearms work, how they are used, how the various kinds differ. You will need to learn a vocabulary of firearms terms.

I recommend that you:

• Get a copy of the "Non-Fiction Writer's Guide" from the Sporting Arms and Ammunition Manufacturers' Institute. It's free and, despite the title, can be useful to the fiction writer as well as the nonfiction writer.
  
  
• Buy a copy of Armed and Dangerous/A Writer's Guide to Weapons by Michael Newton. It's available from Writer's Digest Books.
  
  
• Buy a copy of Gun Digest or Shooter's Bible, in either of which you can find pictures of many modern firearms and information about their features, as well as ballistics data and extensive listings of cartridges.
  
  
• Spend some time at a shooting range with an instructor or a knowledgeable friend who can show you a variety of guns and teach you how to handle them safely. Don't be squeamish. Whatever your feelings about guns, you're a writer -- and this is the best research you can do. If the character in your novel is going to shoot a 9 mm pistol, you ought to know what it feels like to load and fire that gun. It's called writing with authority.
  
  
• Use the Internet, where you can find sport-shooting groups, firearms manufacturers, advocacy groups (on both sides of the gun-control debate), photos and technical data, collectors' clubs, and chat groups. You have a wealth of information available. But as always, you need to know enough to sift out dubious material. That's how the next tip can be invaluable.
  
  
• Line up a contact (better yet, two or three) who has a broad knowledge of firearms and is willing to be a sounding board for you. You might start with a local gun club or ask for referrals from a sport-shooting association. Many people are happy to share their expertise, especially if they know you are trying to be accurate and fair. Such sources can tell you whether a particular gun makes sense in a given scenario.

One caution about that last tip: Don't assume expertise on the part of the clerk behind the sporting-goods counter or the average cop. Many police officers have little knowledge of or interest in guns, except for what they need to qualify with their issued weapons.

By the way, remember my complaint about the novelist who didn't know that Glocks don't have safety latches? Perhaps that sounded like a trivial error. But suppose you were writing a scene in which the bad guy snatches a pistol from a police officer. The bad guy aims the gun at the officer, pulls the trigger -- and nothing happens. The safety is engaged, and before the villain can figure out how to disengage it, the police officer counterattacks. That scene has happened a number of times in real life. But if the pistol is a loaded Glock, it will fire when the bad guy squeezes the trigger.

Your whole scene, and maybe the whole story, can fall apart on that one little point. Check those details and score a bull's-eye in your writing.