Small arms caliber sizes - why 7.62mm

[Gary J]

Ben ..
I'm in "Sunny" Peterborough !!! ...

G.

PS "G", where in the east of England do you live? I lived in Thetford for 9 years before moving to Downahm Market, but now live back in the Midlands

[Ben Evans]

G my wife used to drag me shopping there when we lived at Downham Market, I hate shopping unless for buckles of course

[Dimas]

7.62 caliber is old measurement of 3 lines. The big quantity of a 7.63 Mauser cartridges in Soviet military stocks, and a workshops which are works with calber 7.62 was a starter to produce the pistol ammo, like a mauser 7.63 ( Tokarev 7,62). Firstly the choise of caliber 7,62 was choosen due of a good ballistics.
Here is the link, probably helpful: Russian Section