This topic is a bit far from collecting ammunition, but I’ll still gonna ask since one must know that an intermediate cartridge overbore ranges between 4.29 and 7.99. As its formula says, overbore is equal to the internal capacity (volume) of the case in ml or cubic cm divided by the bore cross section area of the barrel in square cm. Finding the case volume is very easy, but the barrel bore cross section area not. Since most cartridges have this value under 1 square cm (ex. 0.4799 for 7.62x39), how can it be determined?
Thanks for any answers!