What is Calibre?

[BLUEHAWK]

:cd:

Okay, now you infantry are REALLY gonna make fun of me...

What exactly IS calibre? I mean, how is it measured, since there is also millimeter (mm) sizes that are talked about.

Are mm's and calibre the same? If so, then why not just use one or the other?

What is the smallest calibre or mm?

What is/was the largest ever? (I mean like Navy battleship 16 inchers etc)

Does EVERY possible shell have either a calibre or a mm?

When did these type measurements get started in history?

Is there any OTHER type measurement unit that is or ever was in use?

Did cannonballs have calibre or mm?

(I put this in here so you would not think I was afraid of guns)

[Keith_Hixson]

the diameter of the bullet (slug).
The Old English System 30 caliber
Metric System 7.62 mm

Same thing: ie 7.62 Nato or 308 Winchester same bullet.



A 7 mm slug would be a slightly smaller diameter slug than a 30 Caliber slug.
A 8 mm slug would be slightly larger than a 30 Caliber Slug.


For instance: the 30-30 Winchester, 30-06 Springfield, 308 Winchester all shot 30 Caliber Slugs / Bullets.

I hope this helps.

I am not an expert on this subject all shooting weapons have calibers. Weather it is a cannon or twenty-two.

Most modern firearms shoot the 22 Caliber as the smallest Caliber .
.223 Which the M-16 uses is a pretty small caliber
.222 Swift another long shooting small caliber bullet.

I believe (not sure) there are some bullets in the .184 Caliber area.

Sid and Col Murphy know much more about firearms than I do but I hope this helps.

Keith

[BLUEHAWK]

Keith -
But bullets have variable diameters depending on where you measure. Do you measure which end or section?

So, what you are saying is basically that american bullets would be measured in calibre, and other countries (like Britain and european) would be measured in mm?

Do mm bullets fit into calibre rifles?

Its confusing because in my good ole USAF toolbox I learned that mm wrenches DO NOT fit inch-wise nuts and bolts.

From where did these calibres 30-30, 30-06, 308 etc come from, I mean what is the difference between 30-30 and 30-06 for example?

[Keith_Hixson]

1. The hole in the barrel of the rifle (BORE) or pistol, etc is the caliber. The way the slug goes through the barrel is the way you measure the caliber of the bullet.

2. 30-30, 30-06, 308 will all shoot 30 caliber bullets. The difference is the brass casings and how much powder the brass casing holds. 30-30 has a much smaller brass casing than than the 30-06.
However, the 300 Winchester Magnum is also a 30 Caliber Shell.
But it has a much larger casing than the 30-06.

The 30-30 will have a drop of lets say (just guessing) of 16 inches at 600 yds.
The 308 Winchester 12 inches, The 30-06 10 inches, and the 300 Winchester Magnum 8 inches. The larger the brass casing the more powerful and longer shooting the cartridge.


Now, Caliber basically means the size of hole in your barrel or the diameter of the bullet the way goes through your barrel.

.308 is the English measurement of a caliber
7.62mm is the metric measurement of the same caliber.

You are correct that one is metric and the other English measuring system. But both are calibers or diameter of the bore of the barrel.

Now I know Sid and Col Murphy could do better at explaining all of this. I'm a hobbiest not an expert.

One: piece of ammunition is exactly the same:

308 Winchester is exactly the same cartridge as
7.62 NATO Cartridge. No difference that I know of.

7.62 mm bullets can be shot in .30 Caliber Rifles and vice versa its just the measuring system that differs.

Keith

[colmurph]

The British use Lbs. to measure caliber in cannon ie: 24 pounder which would be about 6". We use caliber measured in hundreths of an inch for small arms up to .50 Cal. (1/2 Inch) however we revert to millimeter for everything larger ie: 20mm 37 mm 105mm 155mm but then we fall back to inches for the 8" howitzer then go back to milimeters for the 175 mm and 240mm. Makes a lot of sense huh? The Navy on the other hand uses inches only, ie: 3" 5" 8" 16" but to that they add caliber! as in 5" 38 Cal. In this case the caliber refers to the length of the rifled portion of the barrel. In the case of a 5 inch 38 caliber this would mean that the barrel was 38 times the bore diameter long or 190" long or 15 feet 10 inches. Confusing isn't it? The smallest caliber I ever heard of was a 4mm Kholbri. This bullet was only good for shooting something like a sparrow. The largest I have seen was one that was an 800 mm German Mortar Shell. They have one at Aberdeen and the brass casing is big enough to take a bath in.
The smallest commercially manufactured bullet today is the .17 cal Bee, a wildcat round. (For comparison to diameter, a BB shot is .177 caliber)

[BLUEHAWK]

Keith and Murph -

Amazing, absolutely amazing... I obviously had no idea at all.

Thanks

[PHO127]

There is a variance between lands and groves of some of the same diameter bullets. For instance a .308 caliber bullet is .308 from land to land of the rifle (or 7.62mm) but the grove in the rifling can be different. an AK 7.62 rifle has a deeper grove in the rifiling than a NATO 7.62 therefor the bullet loaded in an AK round is a .311 diameter bullet rather than a NATO 7.62 round which uses a .308 diameter bullet. Also, the designation for ammunition may be such as 7.62 X 39 which is an AK round with a 39 mm case length, versus a 7.62 X 51 which is a NATO .308 or 7.62 with a case length of 51 mm or a Russian 7.62 X 54 which has a case length of 54 mm but is a rimmed case. Confusing, just wait, The black powder ammunition is designated with the bullet diameter such as .44 caliber and the grains (weight) of black powder in the load such as a 44-40 or 45-70. 40 or 70 grains of black powder in the load. Then there is the good old american standby the 30-06. 30 caliber adopted in 1906, originally was the 30-03. then the customs and wildcats, custom bullet loads named after the developer such as a .416 rigby or black powder double rifles such as the .500 or .600 nitro express. The wildcat ammo for custom shooting such as a such as a .308 phoenix. When I started learning how to load my own ammunition I found out that you almost have to be a PHD in physics to figure out how to load and what to load.

[BLUEHAWK]

Pho -
Which is one reason I've never gotten started with it...

Thanks for the info!

[Keith_Hixson]

I have several friends who play around with reloading. Just because you make bullet "hot" doesn't make it better. Some loads will produce great accuracy and others will produce loose flying bullets. Most serious reloaders experiment, and experiment and experiment some more before they get their favorite load to be absolutely accurate.

Keith

[BLUEHAWK]

Guys -
I guess the whole deal for me is that most who've never been in combat or service for that matter, probably think that all you do is get issued a weapon, then some ammo, and then you go shoot people.

The better fighter, it would seem, is the one who understands their weapons the best. Maybe not always, but that fighter would have the better chance of completing and surviving just about any given mission, and also being better able to lead/teach his buddies... some of whom will be just like me; never saw a rifle until basic training, fired exactly one clip of ten rounds at the range (almost made M-1 Expert though!) after half a day of indoctrination , and then never saw another one.

Watching our guys on film or video from all these wars, tells next to nothing technical about their skill and knowledge, to american civilians. We take such pride in our military, most people do anyhow, I'd just like to put myself in your shoes a little bit is all, and the only way I can do that is the way I do everything else... ask a lot of questions, and learn to duck.

Hopefully, one day I'll be able to offer something intelligent when somebody starts spouting off about their opinions concerning what battle is like for the gunners.