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From: grumbly!root@uunet.UU.NET (rb duc)
Newsgroups: sci.military
Subject: Re: USS IOWA
Keywords: caliber
Message-ID: <1990Jun4.194335.4460@cbnews.att.com>
Date: 4 Jun 90 19:43:35 GMT
References: <16213@cbnews.ATT.COM>
Sender: military@cbnews.att.com (William B. Thacker)
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From: grumbly!root@uunet.UU.NET (rb duc)

In article <16213@cbnews.ATT.COM> roth@smoot.enet.dec.com (Lee Roth) writes:
-> ...
->I wondered if the US Navy still had the ability to repair the 16" guns.
->The four Iowa's were the only US ships to mount 50 cal. guns, so spare
->parts are unlikely to be found on the surviving South Dakota class units
->as they mounted 45 cal. guns. 
->Terry L. Fouts

What does 45 cal. and 50 cal. mean?  I always thought caliber was a decimal
inch measurement.  You would either talking about machine guns or
50" guns !!!

rb duc

[mod.note:  For small arms, a "caliber" does mean an inch; a .50-cal
machinegun fires a bullet 1/2 inch (12.7mm) in diameter.
	For larger ordnance, though, the term "caliber" is used instead
to refer to the diameter of the barrel.  The Iowa's main guns are 16"
caliber.  Now, if you divide the length of the gun by its caliber, you
get its length in (are you ready ?) calibers.  A 16"/50 is 16" diameter 
(caliber) and (16x50) 800 inches long.
	The reason this confusing nomenclature is popular is because,
at a glance, you get an idea of the gun's ballistic performance.  If I
speak of the 5" Mk. 10 versus the 5" Mk. 9, you'd have to be an expert to
know the difference; but if I speak of a 5"/25 versus a 5"/51, you'd
immediately expect a higher muzzle velocity, among other things, from
the latter gun.  - Bill ]


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 - -   Richard Ducoty                               ..uunet!grumbly!root
 _]    Capitola, Calif                                root@grumbly.com
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