Guns. Knives. Books.


.9mm or 9mm? .30-06 or 30.06?

Posted on December 31, 2013 at 7:00 AM

I was reading an otherwise excellent crime novel (it will remain anonymous) that used ".9mm" to describe a handgun. It also called a rifle a "30.06." Both stopped my eye as a reader and took me out of the story because both are incorrect.


The right way is "9mm" and ".30-06."


It can be confusing, so here are three rules of thumb when writing any firearm.


1) If there's a "mm" after it, there's no "." before it. Common examples would be 7mm (a rifle) and the 9mm (a handgun). The rule applies even with convoluted calibers like the 7.62x39mm.


2) For handguns and rifles when there isn't a "mm" (that stands for "millimeter," by the way), there's always a "." before it. So it's .22, .223, .270 and the like. If the number is busted up, it's divided by a "-" and not a "." as in .30-06.


3) Shotguns are a little different since they're sorted by gauges. They're written like "12 gauge" or "12-gauge" and "20 gauge" or "20-gauge." Just be consistent. The .410 is different since it's the runt of the litter, and is actually identified as a caliber.


Make sense? Yes? No? Leave me questions in the comments.


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Categories: On Writing Guns

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Reply ★ Owner
9:40 AM on January 4, 2014 
You got it, Dana. It helps keep the flow of the story when those details are correct. I think there's such a thing as a reader's high, sort of like a runner's high, where you get in a groove and devour what you're reading. This stuff takes me out of it like a traffic light to a marathon runner.
Reply Dana King
10:33 AM on January 3, 2014 
Of course it makes sense; common sense. A nine millimeter weapon is nine millimeters, not nine-tenths of one millimeter, as it would be were .9mm correct.

As for inches, caliber is expressed in hundredths (sometimes thousandths) of inches. A .44 is 44/100 inch in diameter; a .380 is 380/1000 of an inch.

It amazes--and pains--me to see how many people who should know better--and claim to know better--make these kinds of mistakes, which only prove they haven't thought even that much about what they're describing.
Reply ★ Owner
8:26 AM on January 3, 2014 
Movies are full of that stuff. I haven't seen 'The Eagle Has Landed," but I will have to now. Another of my favorites is when someone pumps a shotgun for dramatic effect. Yeah, real tough there, buddy, because you just ejected an unspent shell onto the ground!
Reply Joe Brennan
8:17 AM on January 3, 2014 
Speaking of guns there is a scene in the film "The Eagle Has Landed" where Clint Eastwood pulls out a Luger and fires a shot in the air to get attention. He then puts the gun to the head of a German officer and shoots him. Right so what? Well when the last round is fired from this gun, the slide remains back to allow another magazine to be put in and a round slipped into the breach. This is even more noticeable in the Luger because the slide grips rise up as well as going back. When Clint shoots the German he is actually pointing an empty gun at him. Has anyone else noticed this, it has bugged me for years..