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-   -   . Vs mm (http://www.firearmstalk.com/forums/f30/vs-mm-86183/)

zackthatsit 03-10-2013 01:50 AM

. Vs mm
 
Why are some ammo types written with a decimal ex: .22 .38 .45 and others with millimeters ex: 7mm 9mm 10mm

gunnut07 03-10-2013 03:02 AM

because in europe they are not smart enough to figure out real measurements so they have to use idiot proof mm.

Really it is mostly American cartridges are all in inche measurements and forigen cartridges are in metric. It really depends on the devloper and or the marketing department.

c3shooter 03-10-2013 03:29 AM

The creator of a cartridge gets to name it. Those created in Europe were typically named using the metric system. America and Britain, fractions of an inch (.22 is 22/100ths, etc) You will also find OLD names, such as 45-70 that designated caliber of bullet in inch fractions, and the weight of black powder.

Jpyle 03-10-2013 03:38 AM

Quote:

Originally Posted by c3shooter (Post 1170489)
The creator of a cartridge gets to name it. Those created in Europe were typically named using the metric system. America and Britain, fractions of an inch (.22 is 22/100ths, etc) You will also find OLD names, such as 45-70 that designated caliber of bullet in inch fractions, and the weight of black powder.

Thus endith the lesson... :D

BTW there are 2.54 cm per inch and 25.4 mm per inch, just in case anyone wants to compare .XX" to XX mm. For example a .50 BMG would be approx 13 mm (.5 x 25.4mm). :cool:

Caveman556 03-10-2013 03:39 AM

This could be a huge topic. Many make sense, many don't. A quick example is a .38 is really .357....

Trez 03-10-2013 03:43 AM

Quote:

Originally Posted by c3shooter (Post 1170489)
The creator of a cartridge gets to name it. Those created in Europe were typically named using the metric system. America and Britain, fractions of an inch (.22 is 22/100ths, etc) You will also find OLD names, such as 45-70 that designated caliber of bullet in inch fractions, and the weight of black powder.

Quote:

Originally Posted by Caveman556 (Post 1170496)
This could be a huge topic. Many make sense, many don't. A quick example is a .38 is really .357....

C3 pretty much got it there.. The creator of the cartridge gets to name it, even if it doesnt make any sense at all..

The case of the .38 spl is .38 not the bullet. from the days of "Heeled" bullets. ;)

CHLChris 03-10-2013 04:36 AM

I've never understood why it is a .460 Rowland instead of a .46 Rowland.

Why .500 S&W, but .50 AE?

Why .38 special, but .380 auto?

I don't get why the zero is like the silent-p in pterodactyl.

trip286 03-10-2013 05:19 AM

Quote:

Originally Posted by Jpyle (Post 1170494)
Thus endith the lesson... :D

BTW there are 2.54 cm per inch and 25.4 mm per inch, just in case anyone wants to compare .XX" to XX mm. For example a .50 BMG would be approx 13 mm (.5 x 25.4mm). :cool:

I believe a 12.7mm is a foreign answer to our .50bmg. Not saying they're exactly equivalent, just close enough that it's what they built as their equivalent...

Jpyle 03-10-2013 05:38 AM

Quote:

Originally Posted by trip286 (Post 1170620)
I believe a 12.7mm is a foreign answer to our .50bmg. Not saying they're exactly equivalent, just close enough that it's what they built as their equivalent...

yeah...doing the math a .50 BMG, half an inch, is exactly 12.7 mm

trip286 03-10-2013 06:05 AM

Quote:

Originally Posted by Jpyle (Post 1170634)
yeah...doing the math a .50 BMG, half an inch, is exactly 12.7 mm

Oh is it? I thought it was off by a couple hundredths or something.


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