Alright, guys, quick dissertation:
AMMOYou have 7.62mm ammo, which is Mosin Nagant ammo, the
7.62x54r.
All of your 7.62 is currently this. That means your Nosin Magants, AS-F14 rifles, AS-1924 LMGs, AS-1910 MG's, and so on all share the same ammo. In modern terminology, this is "Full powered rifle ammo" and an automatic rifle which fires it would be a battle rifle. 7.62x39, an intermediate round designed for automatic rifles which are lightweight and easy to control but can reach out to more than 300 meters, has not been invented yet.
Your 9mm ammo, which is a larger caliber than 7.62, is basically 9x19mm Parabellum, a small pistol round, which illustrates that caliber does not describe a bullet. We have so far relied references to historical ammunition to clarify what size our cartridges are, but we need to be more clear when making up new ammunition.
In modern terminology, an Assault Rifle is a select-fire rifle using intermediate rounds, and a Battle Rifle is a select-fire rifle using full powered rounds. However, just saying that you're making an assault rifle doesn't necessarily clarify that you're using new ammo.
When you are designing new ammo along with a gun, you should say so specifically. If you simply state that a gun is chambered in 7.62 caliber, it would be natural to assume this is the 7.62x54r, or 7.62 Rifle, that you already have. Instead say something like "new 7.62 Intermediate rounds" or "7.62x38" or whatever new round you want to make. Or if you like naming things by caliber, you could say "New 6.5mm Intermediate Rounds" and from there on we can just say 6.5mm, and know from that name that it's a bullet with much less powder behind it than the 7.62mm.
THIS CONCLUDES THE DISSERTATION