what is the diference of caliber and millimeter in gun ammunition?

Answer 1

Simple. Caliber is "bore" (inside measure of barrel) of the firearm, measured in hundredths of an inch. Its ammunition is the same measure. A "45" fires a round 0.45" in diameter through a gun with a barrel whose inside diameter also measures 0.45.

MM is the same measure, expressed in millimeters.

Simplicity ends there.

Other naming conventions get to be confusing. For example, the standard US .30 caliber carbine rifle used in both world wars and into the Viet Nam era when it was replaced by the M-16. One version of the 30 cal rifle was the 30.06 (thirty-aught-six) and another was the 30.30. Both fire 30 cal rounds. The aught-six refers to the first year of production/use.

Another naming convention is the "magnum." If you ever saw a Clint Eastwood "Dirty Harry" movie, you've heard of a .44 magnum. It's 44 cal, but the powder load is larger, more powerful, called a magnum load. The gun must be capable of containing the higher pressures from the magnum load, so not every .44 cal is a .44 mag.

Another naming convention is "gauge." If you are familiar with shotguns, then you know they are made in different "gauges," i.e., 12 gauge, 20 gauge, 10 gauge. Just to make things more confusing, there is a 410 gauge shotgun, but the 410 is not really a gauge.

Here's a brief history of gauges (from a website):

Shotgun gauges are determined by the number of lead balls of a given diameter required to make one pound of that size ball. Thus 10 balls of 10 gauge diameter are required to make one pound of such balls, or 20 balls of 20 gauge diameter are required to make one pound, and so forth.

This is the traditional, and very old, system.

The actual (nominal) bore diameters of the various gauges are as follows: 10 gauge = .775 inch, 12 gauge = .729 inch, 16 gauge = .662 inch, 20 gauge = .615 inch, 28 gauge = .550 inch. The .410 is named for its nominal bore size, and is not a gauge at all.

(Guage history: http://www.chuckhawks.com/intro_gauges.htm)


Here's another explanation of gauge:

Gauge

Shotgun ammunition is measured in gauge rather than in caliber. Gauge refers to how many lead balls the same diameter as the bore would equal one pound. In the case of a 12-gauge shotgun, a lead ball that exactly fits within the barrel weighs 1/12th a pound. So it would take twelve lead balls the size of the shotgun's bore to equal a pound.

Counterintuitively, the smaller the bore, the more lead balls the same size it would take to equal one pound. So a higher gauge number means the internal diameter of the barrel is smaller, while a smaller gauge number means the internal diameter of the barrel is bigger.

Source: http://www.corneredcat.com/Words/Caliber.htm


So, gauge is simply bore size.

You notice that the smaller the gauge number, the larger the actual bore size, i.e., 10 gauge has a larger bore than 12, 20, 28 (and .410).

Advances in powders made it possible to fire the same weight of shot with less powder and smaller bores, so the 10 gauge that was most popular in the 19th and early 20th centuries gave way to the 12 gauge. The 12 gauge remains the most used worldwide.

Shell length is another important factor in shotgun shells, as the longer the shell, the more powder and the more powerful. And, yes, there are magnum loads.

The shotgun must be rated for the higher power load.

Shot sizes measures are confusing also, i.e., a #6 shot, or a double-aught. Shots may be numbers, letters and buckshot -- all different sizes. What, more confusion?

For more on shot size, I refer you back to this site for more reading:

http://www.corneredcat.com/Words/Caliber.htm


Source: (except for indicated passages on gauge) my past hunting experiences, and over the years I've owned and fired 10, 12, 20 and 410 shotguns, and various rifles and handguns of all calibers.

I'll leave you with one last confusing thought: how do you fire a 22 cal slug through a 30 cal rifle?

Hmm. Okay, here's how.

There are rounds called accelerator rounds, which use a larger cartridge which allows a more powerful load to fire a smaller bullet. I've used a 30 cal rifle to fire 22 cal bullets, and here's how that works.

The 22 round is "jacketed" in a "traveler" (a sleeve which surrounds the bullet and mates to the corresponding rifle bore. As the bullet exits the muzzle, the traveler is immediately stripped and the bullet goes down range at high acceleration (muzzle velocity >3,000fps) and high energy (hits target with great force). Wild little round to fire. You see the impact at the same time you hear the muzzle blast. It's fast.

Answer 2

They are the same, just the unit of messure is different. .45 caliber= .45 of an inch in diameter.

10 Millimeter=10 mm in diameter

Answer 3

Caliber is actually the measurement of a firearm bore in inches; a .45 caliber if .45 inches in diameter.
The same bore can also be measured in millimeters, but that is usually larger weapons, such as military ones.

Answer 4

cal·i·ber (kl-br) KEY

NOUN:

Abbr. cal.
The diameter of the inside of a round cylinder, such as a tube.
The diameter of the bore of a firearm, usually shown in hundredths or thousandths of an inch and expressed in writing or print in terms of a decimal fraction: .45 caliber.
The diameter of a large projectile, such as an artillery shell, measured in millimeters or in inches.

Caliber it is just English measurements in inches.
Like .22 is .22inches of and inches

Answer 5

caliber is measured in millimeters,
just like speed is measured in mph

Answer 6

calibre is inner diameter of the gun expressed in inch(es); the other way is to use millimeter.