caliber/mm conversion
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caliber/mm conversion


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Old 07-31-2012, 01:11 AM   #1
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Default caliber/mm conversion

http://mdmetric.com/tech/cvtcht.htm/

i thought a 7.62 x 51 = .308 cal.
7.62 x 39 = .311 cal
7.62 x 54r = .311 cal.

the above conversion makes 7.62mm = .300 cal.
neither .308, or .311 = 7.62mm


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Old 07-31-2012, 02:08 AM   #2
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We in the USA tend to measure bore diameter across the lands. The Europeans/Eastern bloc measure across the grooves. Trying to make sense of cartridge naming is an exercise in futility. The .44 Mag uses a .429 bullet while the .41 Mag uses a .410 bullet. The .38 Special uses a .358 bullet so it would more appropriately be called a .36 Special?


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Old 07-31-2012, 02:22 AM   #3
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Don`t try to make sense of it, it will drive you NUTS...................
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Old 07-31-2012, 02:28 AM   #4
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Quote:
Originally Posted by sniper762 View Post
http://mdmetric.com/tech/cvtcht.htm/

i thought a 7.62 x 51 = .308 cal.
7.62 x 39 = .311 cal
7.62 x 54r = .311 cal.

the above conversion makes 7.62mm = .300 cal.
neither .308, or .311 = 7.62mm
Unfortunately there is no standard. We still have the .45-70, and the .250-3000.

I've learned the system, but I gave up trying to understand it years ago!
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Old 07-31-2012, 04:01 PM   #5
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Quote:
Originally Posted by 303tom
Don`t try to make sense of it, it will drive you NUTS...................
Words of wisdom right there.
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Old 07-31-2012, 04:42 PM   #6
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do NOT assume that the system makes sense. Much of the naming was done by marketing departments after a 3 martini lunch. .50 Browning Machine Gun is NOT .50 inches in diameter. There are a handful of 9mms - many of which are NOT 9mm. .32 Short Colt and .32 S&W are not the same diameter. Neither is .22 LR and .22 Magnum. And yes, Americans measure a bore one way, Europeans another.

Why ask why? Drink Bud Dry.
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Old 07-31-2012, 06:08 PM   #7
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Quote:
Originally Posted by 303tom
Don`t try to make sense of it, it will drive you NUTS...................
You've been there too?
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Old 07-31-2012, 11:05 PM   #8
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Lazzaroni has the most accurate MM designation. Their 7.82 Warbird is an honest .308 diameter. .308 divided by .03937 = 7.82 MM.
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Old 08-01-2012, 12:36 AM   #9
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Quote:
Originally Posted by billt View Post
Lazzaroni has the most accurate MM designation. Their 7.82 Warbird is an honest .308 diameter. .308 divided by .03937 = 7.82 MM.
But is that measurement taken from the lands or the groover??
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Old 08-01-2012, 01:35 AM   #10
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Quote:
Originally Posted by locutus View Post
But is that measurement taken from the lands or the groover??
The 7.82 Warbird represents the bullet diameter of the round, which is .308.


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