If you multiply .308 x 25.4 which is the multiplier for inches to mm. it comes out to 7.82. So why do we call it the 7.62

Nominal bore measurement of the .308win is .300" [.308 is groove dia.]

.300 x 25.4 = 7.62

Thank you.

Naming conventions for weapons/ammo sometime makes no sense to anyone but the originator...sometimes it makes perfect sense...no rhyme or reason can be applied.

.03937 = 1mm

Or, put another way, 39.37"= 1 meter.

CONVERSIONS... http://www.onlineconversion.com/

.03937 INCHES or " = 1mm...got to keep the nomenclature correct and carry to the correct decimal place...otherwise you miss the moon completely or whatever you're shooting for/at, or make/lose a pile of money in the financial market just like what arbitrage did to some people...

The metric names for calibers are usually done by European naming standards, measured at the lands, rather than at the grooves as is the American standard.

Dan, In general, you are correct, but there are many exceptions.

.. until you get to the American .30 calibres .30-06, .30-40 Krag) and .300 magnum calibres, which all .308 diameter. (and, yes, the Brits started it with the .300 H&H Mag).

Basically many cartridge names are approximations, misnomers and pure blue sky - like the .404 Jeffery - which is .423 in diameter - the .318 Westley-Richards, which is .333 IIRC.

The 38 WCF or better known as the .38-40 uses a .400 -.003 bullet used with a .394 bore and a .400 groove diameter.

The cartridge name is known as nomenclature.
It does not necessarily exactly correct.

See what I mean...!!!!

Beware that artificial INCH (that was a made up thing when we Brits made the rifles here that was known to everybody else as the "Enfield Inch".

Which wasn't an inch. But something that was near enough for when the dimensions of the plans for some such weapon were transcribed.

Or some such reason that I've forgotten. But that the late Herb Woodend would know.

Or...here:

http://www.rsaf-aa.co.uk/rsaf/...age/enfieldinch.html

quote:

Originally posted by SR4759:
The cartridge name is known as nomenclature.
It does not necessarily exactly correct.

like a 38 special or 44 mag ....