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.
Fourth of July 2015 Weekend Update: America!
@benjaminsobieck For the first one, the correct measurement is .354 inches. #ImperialForever
— Nate Hoffelder (@thDigitalReader) July 1, 2015
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Can’t imagine getting hit by a .9mm gun would be all that noticeable. But one can easily see the confusion, with .45 and .38 cartridges being used in other pistols. Just one more instance of the rest of the world not realizing they should be using inches instead of that old-fashioned metric system. : p
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The lack of consistency with firearms in general certainly doesn’t help. For a while in the late 1800s and early 1900s, manufacturers would name models by the year produced. It’s pretty easy to track the Tommy gun over time with model names like the 1921, 1928, etc. But somewhere along the line, someone got the idea that that was too simple. I don’t know who got to decide which calibers were inches and which were millimeters, but I think the joke was on us.
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Thanks for this.
I’m trying to self publish an action adventure novel and had originally written everything out like this.
But when I got it back from the copy editor (who I paid to look at stuff like this), they proceeded to inform me that the Chicago Manual of Style puts a SPACE between the measurements! ( 9 mm )
Needless to say I will be fixing everything before publishing.
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CMS can bite it. 9mm is the way to go.
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I’m helping with an auction catalogue and was wondering if it is appropriate to abbreviate gauge to GA or ga….for instance 12GA or 12 ga. Thanks in advance for your quick response.
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Either works for an auction catalog. Pick one and stick to it.
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Thank you! As an official court reporter in criminal court for many years, I have always struggled with this!
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Glad you found it helpful!
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Thank you for the valuable information. One question though.
How would you write the plural for a .22 caliber rifle? Or a .308, etc.? As in this sentence: “I have several .22s, two .410s and . . . .”
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I’d do it just like that. I know the temptation is there is to stick an apostrophe before the s, but your example is right on.
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I’m writing a story about the apocalypse, and wondered how to go about writing sixty caliber, or 60ca. Thank you!
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Perfect. Thank you for having this information. Just what I was looking for.
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