In this listing of the specifications of the Browning Hi-Power Mk I, immediately below the standard muzzle velocity entry (of 350 m/s) there is also another listing for velocity. It is abbreviated as: “V[sub]12.50[/sub]” (and gives a figure of 340 m/s).
I’ve not seen the term V[sub]12.50[/sub] before. Although I’m sure it’s defined on a webpage somewhere, damned if I can find it. So I’ll ask here: anyone know what it is?