I have done lots of successful metrication edits on www.wikipedia.org

I was also converting weapon calibers for example converting:
".50 machine gun" to "0.5 in (12.7 mm) machine gun'

I was aware that before 1954, the British and Americans disagreed about the
size of an inch but was ignoring that (I claim 'translators licence') and
simply converting using the google converter which uses the 'international
inch' of today.

However, I received some feedback that I would like some help with. This is
what was said:
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Re: your edit on the Northrop YB-49 page. Note that .50 is an ammunition
calibre and there is not always a 1:1 correspondence between metric and
imperial calibres. For example, the 7.62 mm NATO round is not equivalent to
a .30 round - it's a .308, and guns designed for the 7.62 can fire a .30
round only if specifically modified to do so. Similarly, the 5.6 mm NATO is
a .223 round. 
The problems arise because different weapon and ammunition manufacturers are
measuring different things when they specify calibre. If we were to try
standardising, we would have to decide on an independent, arbitrary
standard. IMHO, best practice is not "translating" calibres. 

Note too that imperial calibres are most conventionally specified as .50,
not 0.50 in (which might be the same as the weapon's bore, but also might
not be - in the case of the M2 or M2-derived guns on the YB-49, it just
happens to be true although this isn't a given). 

Artillery and naval guns are a whole other ball game though, and are
conventionally specified as bore diameters. I'm not sure that I would
convert those either, though. Note that the US Army specifies its howitzers
as 105 mm and 155 mm, not 4.13 in and 6.10 in. 
********************************************

-- 
Terry Simpson
Human Factors Consultant
Connected Systems Ltd

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