4 mm may refer to:
*
4 mm caliber
This is a list of firearm cartridges which have bullets in the to caliber range.
All measurements are in mm (in).
Rimfire cartridges
Centerfire cartridges Pistol and PDW cartridges
Revolver cartridges
Rifle cartridges
See also
*.17 ...
, gun cartridges between 4–5 mm diameter
*
4 mm scale
4 mm scale is the most popular model railway scale used in the United Kingdom. The term refers to the use of 4 millimeters on the model equating to a distance of 1 foot (305 mm) on the prototype (1:76.2). It is also used for military mo ...
, in rail transport modelling, 1:76.2 scale with rails 16.5 mm apart, representing standard gauge in Britain
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