Quote Originally Posted by steve medlock View Post
In the English convention, the calibre is the diameter of the barrel measured from land to land.
Steve,

How then do we explain the differnce between .303 and .308?

.303 is measured as the smallest size through the barrel, ie a ball of .303 diameter will drop through the barrel, bullet diameter is .311/ .312

.308 is the maximum diameter through the barrel, ie bullet diameter

Steve