Because somebody asked:
A 30-06 (and its cousin, the 30-30) are more like a third of an inch.
Generally, weapons are measured in hundreths of an inch (.50= ~half an inch)
or metrically (the 5.56mm round of the M16). A good conversion is to
multipy the metric by 4 and shift the decimall two places to the left;
5.56mm =~.223.
As for examples:
9mm=very accurate, pretty powerful pistol round. Also used in many
SMGs (like the Uzi).
10mm, 11mm=major power; these are the guns that will knock a large
hole in you and knock you down to boot.
7.62mm: fired from the M60 and many other light-mid sized machineguns
used by the US and most of NATO.
5.56mm: used in the M16 and other Western weapons (like the M249
SAW).
5.45: Used by Eastern European forces in their assault rilfes and
scaled versions thereof. Most of the AK series.
7.62 (again) The Russians used a slightly different calibre, differing
primarily in length.
More, but I have little time.
J Roberson