What sort of systemic gameplay you do get out of spending CPU and GPU cycles to draw and process the process of bullet being actually loaded into the gun?
Their bullet stuff is part of physicalized inventory. Same system in which you will be able to hit weapon, destroy its tube so it will be blocked and that gun receiver will blow up then once that bullet goes off. Moreover once armor system will be in things will lose its HPs and everything will be based on physical damage. So for example armor will have its own penetration values and different type of bullets will have different penetration etc.
Right now game still uses normal bullet system and mags equipped are just for show so if you have 2 mags with 30 bullets each you shoot 15 you can change mag until you run out of bullets. With physicalized inventory update in 3.15 those mags will be what you have and if you leave 10 bullets in chamber those 10 bullets will be wasted.
Amount of mags you will have on you will depend on armor being used and storage space you have. For example mags you can use are on you and you can see them which means you can target someone granade or mag. If you have 6 mags those 6 mags will be around your belt.
If you run out of mags you will be able for example to strip mags out of bullets and refill yours.