Uh... Have you guys played ARMA Reforger with the WCS Mod? So in that mod you use modern (to date) gear like plate carriers (WITH PLATES). When you shoot someone with plates on... It kind of take alot to kill them. The only thing that is happening in BF6 is that they are not passing out from taking thoracic blunt force trauma (That's super hard hits to the chest and stomach for you kids who haven't done anatomy/physiology)
So, the ammo expenditure for a kill is pretty good actually. Immerse yourself in some self-role play "I shot the hell out of his chest! Must have been all plate hits. :( "