If you wander over to Rickard's Mystery Circus, take my advice and don't eat the peanuts. But do read Steve Mosby's piece on guns. Steve is one of our UK friends, and as such, doesn't have the God-given right every free-breathing, flag-loving, third-world-stomping Amerkin has to blow his (or her) foot off with the sidearm of his (or her) choice.
I don't know how they stand it.
Over here, in the Greatest Country Ever™ we can pack heat to the supermarket and in Florida, if some crunchy granola type scoffs at the high fructose content of your Captain Crunchberry, you can blow her self-righteous shit away right there in the cereal aisle.
But I digress.
If you write crime fiction, the issue of guns is bound to come up sooner or later. How you handle it is up to you. Some writers prefer to ignore all but a gun's basic function. For instance, Kevin Wignall's assassin shoots people on a regular basis and has the good character to feel bad about it, but I don't remember a thing about his firearm except a hazy recollection that it was a semiautomatic. And I could be wrong about that.
On the other hand, Dirty Harry carries a .44 Magnum, the most powerful handgun in the world, and can blow your head clean off, except that it's not the most powerful handgun in the world any more, but that's OK because he's Dirty Fucking Harry, so I'm not going to be the one to tell him.
If you write books like Stephen Hunter, you better know your guns, because his readers expect him to know about grains, riflings, scopes, windage and all the other things that go into lethal hardware.
I tend to work in the middle here somewhere. For instance, I can tell you what type of gun my character in the new book carries, and what type of gun he finds in his daughter's purse, but I keep it pretty simple. He carries a Colt .45 and she slips a a Mauser .32 into her handbag every morning.
You can write about guns and still keep it simple if you know a few facts. The Internet is good for finding out caliber, number of rounds, etc. Knowing how many bullets a gun carries could be important to know in a shoot-out, unless you're Hopalong Cassidy and can shoot the same six-shooter all damn day without reloading.
A few details might, or might not be important. For instance, that Colt .45 weighs nearly three pounds when loaded, which makes it a bear to carry all day. I know, I lived with one on my hip for two years and they'll wear your ass out.
On a more general basis, this all goes to how much research should you do, about anything. I'd say, if it's important to your story, or it can help identify something about place or character, then use it. If all you're doing is showing off, save it for the bar. I once ground a novel to a dead stop by showing how much I knew about sailing.
There's a really good example of this firearms business in the movie Ronin, when DeNiro's character is asked about his favorite gun. DeNiro says it's a 1911, which is the traditional Colt .45 semiautomatic. That answer tells us a lot about DeNiro's character, and the character of the guy who asks the question. Do you, as a casual film goer, need to know about the 1911 to get it? No, but if you do, the film is richer, and the exchange means more than if you don't.
If you want to write safely about handguns, here are a few general rules:
1. Revolvers are those guns with a big cylinder in the middle that hold the bullets. Most of the revolvers you see plainclothes cops or 40's detectives packing are snub-nosed .38s and generally carry five rounds. But if you have your guy packing six, you'll be OK.
2. The big semiauto you see in war movies and gangster flicks is almost always a .45. They load from a magazine pushed into the grip from the bottom. To load the round and get the gun ready to fire, you have to pull back the slide and then you're good to go. When the gun is empty, the slide locks back, making it easy to see.
3. Silencers only work on automatics because too much of the sound escapes from around the cylinder of a revolver to be effective.
4. There are no safetys on revolvers.
5. There are exceptions to every one of these rules.
But if you stick to these, you'll generally be OK.
If you do use a gun in your writing and you don't know anything about them, that's OK, too. Just don't use it as a pivot for a plot point or in an action sequence. Because if you screw a silencer onto a revolver, a lot of people are going to say WTF? and assume you don't know what you're talking about.
Or you live in the UK.
Really, what do you guys do when you get roaring drunk and want to let off a little steam in your neighbor's direction?