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Caliber Discussion


Joriko
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You're not asking much! :lol: There are enormous numbers of different calibers!

Formally, caliber refer to the diameter of the inside of the barrel.

However, "caliber" is often used to describe the entire cartridge: A 7.62x25mm is a pistol cartridge used in the Soviet Union around WW2, while the 7.62x39mm is the far more powerful cartridge used in the AK-47. The "x25mm" and "x39mm" refer to the length of the cartridge case. Both have a diameter of about 7.62mm, but that's the only similarity.

US and British rounds are sometimes measured in decimals of inches: A .30 caliber bullet is 0.30 inch in diameter (approx. 7.62mm).

In addition to the difference between just measuring the diameter and taking the whole cartridge into account, these designations sometimes "cheat" to distinguish between cartridges of the same caliber:

The .38 Special is a revolver cartridge as is the .357 Magnum. The bullets are in fact of the exact same diameter and differ only in the length of the cartridge case and the amount of gun powder they can hold. You can in fact fire .38 Special rounds from a .357 Magnum revolver, but not the other way around. Another example is the US 106mm recoilless rifle (used after WW2) which was actually 105mm, but the caliber designation was changed specifically to avoid confusion with other 105mm weapons since the ammunition was not interchangeable.

To make things even more complex, the same cartridge may have several designations: 12.7x99mm, .50 Cal. and 50 BMG all refer to the same cartridge: The one used in the US M2 heavy machinegun. And the .32 ACP and 7.65x17mm refer to the same cartridge, typically used in small handguns like the Walther PPK (the one James Bond used to carry).

Anyhew, Wikipedia is a good place to start and I'm sure there are plenty of gun nuts on this forum that are able to answer any question. :)

Respectfully

krise madsen

Edited by krise madsen
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I cannot stand Wikpedia, they post so much garbage on that site.

I would ask at a gunshop on a slow day and actually look at the rounds.

The only thing I would have to question Krise on is that I have always known the .38 special to actually have a .38 measurement (not the bullet, but the casing), and that it is not just a random number they came up with. Maybe I am wrong, but this is what I have always understood it to be.

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I cannot stand Wikpedia, they post so much garbage on that site.

I would ask at a gunshop on a slow day and actually look at the rounds.

The only thing I would have to question Krise on is that I have always known the .38 special to actually have a .38 measurement (not the bullet, but the casing), and that it is not just a random number they came up with. Maybe I am wrong, but this is what I have always understood it to be.

I didn't explain that part very well, sry. I'm sure you're right about the measurement. What I meant was that to the layman it would seem that the .38 and .357 have different caliber barrel/bullets when in fact they are identical.

Respectfully

krise madsen

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I cannot stand Wikpedia, they post so much garbage on that site.

I would ask at a gunshop on a slow day and actually look at the rounds.

The only thing I would have to question Krise on is that I have always known the .38 special to actually have a .38 measurement (not the bullet, but the casing), and that it is not just a random number they came up with. Maybe I am wrong, but this is what I have always understood it to be.

I didn't explain that part very well, sry. I'm sure you're right about the measurement. What I meant was that to the layman it would seem that the .38 and .357 have different caliber barrel/bullets when in fact they are identical.

Respectfully

krise madsen

Okay, that was what I thought you meant, but I was just not sure as you did not really state that. :thumbsup:

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  • 1 month later...
What I meant was that to the layman it would seem that the .38 and .357 have different caliber barrel/bullets when in fact they are identical.

Respectfully

krise madsen

Krise is correct, if you take a micrometer and measure the diameter of both bullets they will measure +/- 0.002 to 0.357. The difference as he stated is the .357 is a longer cartridge (shell case), give it the ability to hold more gunpowder and thereby be more powerful.

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What I meant was that to the layman it would seem that the .38 and .357 have different caliber barrel/bullets when in fact they are identical.

Respectfully

krise madsen

Krise is correct, if you take a micrometer and measure the diameter of both bullets they will measure +/- 0.002 to 0.357. The difference as he stated is the .357 is a longer cartridge (shell case), give it the ability to hold more gunpowder and thereby be more powerful.

That was not the question at hand. The question was how the rounds were designated, and the fact that they are simply measured differently. The point was that the .38 is the measurement of the diameter of the casing, not the round, so the designation of .38 is not simply arbitrary, but it actually does represent something.

It was not clear to me in Krise's original post, and I thought he was saying that the .38 designation was arbitrary, when in fact he did not mean that.

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That is not correct for modern cartridges, but was correct when it was first developed. Back then the bullet was also the same dia as the casing or cartridge, (See Heeled Bullet) and had a tail on it that allowed it to be inserted in to the casing. But that has not been the case for about 100 years now. They changed the way they designed the .38 sometime after the invention of smokeless powder in 1884. While the bullet became smaller the designation stayed the same as they saw no need to change it. When the .357 was developed in 1934 in response to Colts Super 38 they made one change which was to make the cartridge longer to prevent loading the higher power .357 in to an older .38.

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  • 2 weeks later...

That is not correct for modern cartridges, but was correct when it was first developed. Back then the bullet was also the same dia as the casing or cartridge, (See Heeled Bullet) and had a tail on it that allowed it to be inserted in to the casing. But that has not been the case for about 100 years now. They changed the way they designed the .38 sometime after the invention of smokeless powder in 1884. While the bullet became smaller the designation stayed the same as they saw no need to change it. When the .357 was developed in 1934 in response to Colts Super 38 they made one change which was to make the cartridge longer to prevent loading the higher power .357 in to an older .38.

I did not say that it was for modern cartridges. The whole point of the post was HOW things were designated, in the PAST AND THE PRESENT, so that Joriko could better understand why certain cartridges that are the same in diameter are labled differently. I only posted to clarify something Krise posted, as I was not sure exactly what he was saying.

I am not trying to give you a hard time, but try reading the whole thread next time before you post. :thumbsup:

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