When it comes to the assault rifles, this is my observation. I have no numbers to back this up, and it’s subjective to how I play the game. Your results (or opinions) may vary.
For me, the AG4 is generally ok and versatile, but not great at anything. It’s a bit slow on rate of fire, has a lot of recoil and is hard to control in full auto. But it seems to do the most single shot damage of the 3 rifles. In full auto, not a lot of your rounds hit their target, even at closer ranges. However, when equipped with a barrel extension, it seems to have decent range and when used with a scope in semi-auto, can be an effective short range marksman rifle. It can also take vision modules which is super helpful. I think that’s it’s strongest advantage overall.
The AI-76 is a beast. It has a high rate of fire and is more controllable in full auto than the AG4. It has a nice range with the barrel extension as well, but can only take the ACOG. so you don’t get vision module capability or magnified optics. This rifle delivers the most damage you can deal theoretically due to its high rate of fire, but still has a lot of recoil. There will be a lot stray rounds at longer ranges. It makes it less effective at medium to long range when used full auto. 3 round burst helps accuracy a at medium ranges somewhat. At close range, it tears anything up. Especially hunters.
The AG5 is a balanced gun. It fires a lower power cartridge that does significantly less damage per shot. But it’s got a really high rate of fire and is pretty easy to control on full auto compared to even the SMGs. This combined with higher velocity rounds makes it the most accurate medium-long range full auto weapon. So its DPS is actually fairly high due to shooting faster and more rounds landing, although not as much as what you can get at close range with the AI-76 where you can land all your shots.
When it comes to comparing in-game guns to the real world, the weapon stats in the game can take some liberties with reality. In real life a .50 cal AP can put a hole the size of a golf ball clean through an truck engine block 1 km away. In GZ, it won’t even dent runners or seekers unless you hit their weak points. I think the assault rifle stats make sense compared to each other and are somewhat realistic. I really have no issue with they way they’re currently balanced.