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GAgunLAWbooklet

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The Hen that laid the Golden Legos
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Decimal points belong in written expressions of a gun's caliber.
Since all the guns we own have bores of less than one inch in diameter, every time we type a caliber online it is correct to use the decimal point. That shows that the "caliber" being described is actually a fraction of an inch.

.45 caliber is nominally 45/100 of an inch.

.30 caliber means the hole in the bore, before any rifling grooves are cut into it, was drilled with a 0.30" bit.

A 9mm is not really a "caliber" although we may call it that in common usage, instead of saying "9 mm bore cartridge" or something weird like that. We might say we carried three "caliber" guns to the range today-- a .38, a 9mm and a .40. We might say our newest concealed carry gun has a "caliber" of 9mm. Thats no big deal. I'm not criticizing that. It's a technicality.

What I will criticize is sticking a decimal point in front of a millimeter-designated metric cartridge. A millimeter is a tiny thing, like the thickness of a grain of Uncle Ben's rice. All the guns and bullets we talk about here online are GREATER than one full millimeter. In fact they'll all be over 4 mm, as the smallest-bore cartridges I know of are the .17 calibers, and they're nominally 4.5 mm.

Therefore, don't call your 9 x 19 mm pistol a ".9 mm" unless you want to look like an ignoramus who doesn't know the difference between an inch and a millimeter, or has no idea what that little dot that looks like a period means when used with numbers.

(If you've forgotten 3rd grade math and need a reminder what a decimal point is, click this link to watch a helpful video:

https://www.khanacademy.org/math/ar...iew-decimals-intro/v/introduction-to-decimals
or this one:
https://www.khanacademy.org/math/ar...ith-review-decimals-intro/v/decimals-as-words
 
If you say you've got a .10 millimeter pistol for sail, that means your gun shoots bullets are 0.1" millimeter wide. One-tenth of one millimeter. It would take ten of your bullet diameters stacked on top of one another to reach 1.0 mm, and 90 of them would equal the width of a 9mm bullet.
 
Now SHOTGUN GAUGES are another thing that confuse people.

Most shotguns and ammo they fire are described in "gauges" which is NOT a caliber. It has nothing to do with saying how wide the bore is in inches, or fractions of an inch, or the decimal equivalent of that inch fraction.

A "gauge" in the gun world means how many pure lead balls of exact bore diameter would it take to add up to a pound of lead.

10 gauge (also called "10 bore") means each perfectly-fitting lead ball would weigh 1/10 of a pound.

20 gauge would use lead balls that weigh half as much, so it takes 20 of them (not 10) to make a pound.

.410 isn't a gauge, it's a caliber. Just like you'd use for describing the bore of a rifle or pistol in English units based on the inch.

But for "GAUGES" you don't use a decimal. They're all more than one.

A " .20 gauge" gun, (that really is 1/5 of one gauge) would have a bore so wide that one single lead ball that fits down its barrel would weigh 5 lbs. That would be a cannon with about a 2-inch bore, I think.

So it's just "twenty gauge." Not "point-twenty gauge" or "period-twenty gauge."
 
Thanks for hearing me out.
I hope my .5 posts in this thread have been helpful and informative.
Now I'm going to put on my size .11 EE boots and go out to my Nissan .300ZX, fire up that .3 Liter engine, and drive away (but not too quickly. The speed limit on the road in front of my house is .40 mph.)
 
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