"30 cal 1906" which was previously 30-03 (30 cal 1903) which is .308 bore diameter
308 Winchester .308 bore diameter
and then we have 32-20 ......32 cal 20 gr of black powder..... or 47-70..45 cal 70 gr of black powder...or 30-30 which was never intended to use black powder
and the 7 x 57 (as an example of Euro metric designations) 7 mm x 57 mm case length
or howza bout 38 spec 38 cal groove to groove..... 357 mag same diameter but measured land to land
confused yet?
Well so are most people so don't feel bad...
