Gauges/calibres


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The Deer Hunter
December 28, 2006, 11:20 PM
My friend asked me what a calibre is. Is it just the measurement in decimals of an inch?

Also what is a gauge? I recall reading about how a gauge is measured. I think its something like lead round balls with the bore measurement...

So please inform me.

Thanks.

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isp2605
December 28, 2006, 11:24 PM
Is it just the measurement in decimals of an inch?

Correct and it could also be millimeters.

Also what is a gauge?
You got it about gauge. It's the number of lead balls the diameter of the bore equal to 1 lb. So a 12 gauge would be 12 lead balls the size of the bore to equal 1 lb. 20 ga would be 20 lead balls the size of the bore. 10, 16, 28, etc figured the same way.

stoky
December 28, 2006, 11:27 PM
Caliber is as you say, the bore diameter in inches or millimeters.
Gauge is how many lead balls that size it takes to add up to a pound. (.410 excepted)

Froggy
December 28, 2006, 11:29 PM
Spot on.

And since we know the "weight" (specific gravity) of lead, you can convert them:

12 gauge --> 0.729"

20 gauge --> 0.615"

28 gauge --> 0.550"

gbran
December 28, 2006, 11:41 PM
Then there's the oddball 410.

Avenger
December 29, 2006, 03:30 AM
I've always thought that, at least in engineering terms, calibre is the ratio of bore and barrel length, or bore and chamber length for the cartridge.

ArfinGreebly
December 29, 2006, 04:59 AM
Yes indeed.

The .410, though often called a "gauge" is, in fact, a calibre, and refers to the bore diameter in inches.

Not altogether amazing, then, that certain rifles and pistols are chambered to fire both .45 LC and .410
(for example:
http://www.thunder5.com/docs1.html
http://www.galleryofguns.com/Shootingtimes/Articles/DisplayArticles.asp?ID=39
. . . there may be others).

RKellogg
December 29, 2006, 07:48 AM
I had an old timer tell me that the 28 ga was the perfect gauge , mathematically . He also said the same about the 7mm mag . Any one care to explain why .

deadin
December 29, 2006, 11:11 AM
I've always thought that, at least in engineering terms, calibre is the ratio of bore and barrel length, or bore and chamber length for the cartridge

That's true if you're talking about naval guns. (Like a 5 inch 58). I've never seen it applied to small arms.

Dean

isp2605
December 29, 2006, 11:27 AM
I had an old timer tell me that the 28 ga was the perfect gauge , mathematically . He also said the same about the 7mm mag . Any one care to explain why .
You should have asked him. It was his story.

deadin
December 29, 2006, 12:10 PM
To confuse the "bore diameter" issue. Some are the diameter measured to the grooves (i.e. .308) and some are the diameter measred to the lands. (i.e. .303 British).:evil:

Dean

JesseL
December 29, 2006, 12:39 PM
deadin:

And some have very little to do with any real measurements at all. .380 ACP is .355", .38 Special is .357", .44 Special and magnum are .429", and most 32s are actually .308-.311".

deadin
December 29, 2006, 12:54 PM
Some of those can be explained (original heel seated bullet diameters, etc.)
Some are beyond explaination.;)
That's why I keep a copy of "Cartridges of the World" on hand.:D

DoubleTapDrew
December 29, 2006, 03:25 PM
Isn't "calibre" the English spelling and "caliber" American? Kind of like tire and tyre?

It's funny when talking to newbies about calibers and how 380 or 357 sound massive compared to 38 or 32 until they realize there's a decimal in front of there.

What caliber is the phased plasma rifle in the 40-watt range? :p

CWL
December 29, 2006, 06:04 PM
Guage and bores of firearms was originally determined 500-600 years ago, that is why it seems so strange to us today.

The weight of shot was originally determined in the 15th-16th Centuries using Imperial Roman weight measurements. This was the only uniform measurement for weight back then because each country, duchy, county, town & village could have it's own method of measurement. One pound of lead could be divided into 1/20, 1/16, 1/12, 1/10 etc. these measurements determined the size of a bullet and the bore diameter (guage) necessary for the arquebus, musket and pistol made by any gunsmith. This also explains how pistol calibers came about: .36 = 86 balls/lb; .44 = 48 balls/lbs.

Mannlicher
December 29, 2006, 06:16 PM
I've always thought that, at least in engineering terms, calibre is the ratio of bore and barrel length, or bore and chamber length for the cartridge

well, with naval guns, caliber refers to the length of the barrel. The US 16 inch guns on the Iowa Class BB for example, are 16", 50 caliber. The barrels are 67 feet long.

Mal H
December 29, 2006, 07:05 PM
What caliber is the phased plasma rifle in the 40-watt range? :p It is around 6600 angstrom units, give or take a few hundred. :p :p

GunnySkox
December 29, 2006, 07:11 PM
One thing I noticed about gauges is it's sort of like the fractional end of the "pounder" system used for smoothbore cannon. Observe:

A smooth-bored cannon called a "three pounder" has a bore of a size that fires a projectile of a certain composition and form which weighs, you guessed it, three pounds.

A smooth-bored arm called a "twelve gauge" has a bore of a size that could fire a projectile of a certain composition (lead) and form (sphere) which weighs, and here's the style, 1/12 of a pound.

Am I right?

~GnSx

45crittergitter
December 29, 2006, 08:03 PM
Note that caliber by definition is the expression of diameter in decimal parts of an inch. For example, it's "44 caliber," not ".44 caliber," as the decimal point is redundant with the word "caliber."

Billll
December 29, 2006, 09:17 PM
Here is a gauge/caliber chart:
Gage Ball dia
425 0.220
290 0.250
169 0.300
140 0.319
100 0.357
66 0.410
53 0.441
50 0.450
28 0.545
20 0.610
16 0.657
12 0.723
10 0.769
8 0.828
6 0.911
5 0.968
4 1.043
3 1.148
2 1.314
1 1.656
0.75 1.822
0.5 2.086
Note where some of the more popular calibers fall, 45, 357, 410, 44.
The density of 'lead' varies a bit with alloy, so if you set up a spread sheet to calculate this, keep it in mind. These sizes are not absolute.

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