TL;DR: The current calibers in-game are a mess, and screw up anything from ammo management to weapon balance. We need to pick a direction and follow it.
When I first started playing GZ, with just the basic game installed, I found two types of 9mm: one for handguns and one for SMGs. This made sense for me, since IRL there is a distinction where higher loadings can damage a pistol, but lower loadings can prevent an SMG from cycling properly. Separating the ammo pools also made gameplay sense, since otherwise 9mm would be a “semi-universal” ammo pool capable of feeding a very good pistol and two very versatile SMGs that can tackle very tough enemies later on. After all, most other guns in the game also have very specialized ammo pools, such as only the Walther PP using .32ACP, or only the Sako 85 using .243.
…But then I progressed further into the game and found that the AG4 (a.k.a H&K G3) and the AI-76 (a.k.a AKM) are listed as using “7.62”, when in reality they use two different cartridges (the G3 uses 7.62x51mm NATO, while the AK uses 7.62x39mm Russian). But since at first I thought both filled a similar niche (…more on that later), it felt like an “acceptable compromise”, though still a very odd departure from the “realism-grounded, one-gun-one-cartridge” approach of the other basic guns.
…Then I progressed further and downloaded the DLCs and it all became a complete mess.
Let me summarize this mess in one example: the game currently has 7 weapons using the same “7.62mm” ammo pool (the G3 and AKM from the base game, plus M21, M60, PKM, Dragunov SVD and Mosin Nagant from DLCs), but in reality they use 3 vastly different cartridges (the AKM uses the weaker 7.62x39mm, the G3, M21 and M60 all use 7.62x51mm NATO, and the Mosin Nagant and the PKM use the beefier 7.62x54mmR). This means these guns should behave vastly differently in damage, recoil, accuracy, penetration, etc etc, but… they’re somewhat squished together in a very uncharacteristic way.
Heck, the Dragunov SVD uses the more powerful 7.62x54mmR cartridge yet it deals less damage per shot than the M21, which uses 7.62 NATO? And yet the M21 has FAR more recoil and muzzle climb than the G3 despite using the same caliber and having better ergonomics?
And as another gameplay consequence, you can have a huge variety of guns that cover different scenarios while all using the same ammo type. Need an SMG? The AKM with the best mag upgrade and a suppressor can fit the bill. Need a battle rifle? G3 with a 1-4x scope. Need a sniper? Mosin Nagant with your best scope. Need a bullet hose that kills everything? Take your pick between the M60 and the PKM.
What I mean here is that we have a clash between two approaches: “differentiate for the sake of realism and challenge” or “aggregate for the sake of simplicity”. The game seemingly started with one approach, and now dove head-first into the other, woefully unbalancing its own guns (the Dragunov is DESPISED by many players, and many still have a hard time justifying the existence of the M21).
How to solve this problem? Well, merely “picking one style and sticking to it” is not a simple thing, since the gameplay balance implications are VERY widespread (they affect how many ammo types people have to carry, how many cartridges the game has to ballistically simulate, how many guns some players will decide to carry for each role, etc etc). But regardless, this problem needs to be tackled, so we can have some sense of balance and/or utility in the game’s guns – even if this means some guns will be used as merely “progression stepping stones” (which in itself is a subject for a different thread) – but as it is, by the time a player manages to drop a 5-crown M21 with enough damage to one-shot a runner… they probably already have disassembled at least a dozen Barretts and maybe a few Mosins. …And the starting Sako85 can already one-shot the runner’s fuel tank anyway.
So in short… the current cartridge/caliber system is a mess because it seemingly grew up unchecked and without a clear direction. It’s about time a direction is taken, so other issues can be remedied with it.