and

http://www.convertunits.com/from/mm/to/caliber

How many mm in 1 caliber? The answer is 25.4.



so a 45caliber 1911 is actually .45? <mind blown>



so a 50mm dessert eagle is actually.. wait.. or is that 50cal?



see, so confusing.



why 2 metrics?

wished the gun manufacturers got together to had a standards consortium

 

One is metric (mm) the other is US/Imperial (Cal). Caliber is actually hundredths of an inch, hence the 25.4. There are 25.4mm in an inch. A 45 Caliber is .45". Desert Eagle is a 50Cal. A 50mm round would be almost 2". A 30mm round (like what the A-10 fires) is Almost 1.20".

 

Gun makers did get together and make standards. The standard is: if a country adopts a caliber, we'll make guns chambered for it.



Here's one to really mess with you, if you have trouble with .45 and 9mm ... .223 Remington vs. 5.56 NATO, or .308 Winchester vs. 7.62 NATO.



pIvKZxD.gif

 

And a .38 Special is the same caliber bullet as a .357 Magnum, both .357 in diameter. .38 Special cartridges can be used in a .357 Magnum revolver but a .357 Magnum can't be used in a .38 Special. a .44 magnum is really .429 and .45 Colt is ,454 in diameter while a .454 Casull is actually .452 in diameter.



It's totally bizarre. There are a few reasons for some of these but really there aren't many good excuses. I've always preferred the metric nomenclature of Xmm x XXmm. It gives you a pretty good approximation of what power and ballistics a cartridge will have.

 

because.. 'Merica.