While playing today in Texas ...Teamplayers... server on Kashan, my US tank, the Abrhams, showed that as soon as I got into it it had no ammo for the 7.62 machine gun. It also made the tell-tale clicking sound of an empty chamber when I right-clicked. However, when I right-clicked (while it was making the clicking noises) my squadmates told me that I was indeed firing my weapon.
When I "fired" I could see no tracer, and no puffs of bullet impacts were visible to me, although my squadmates observed all these things. I was able to kill enemy infantry by just spraying them with machine gun fire, but it was hard to guide bullets in without the tracers.
Thank you for your time.