Golden mag not reloading by it's own on CAR smg

I was in the training field when I noticed that the CAR smg with any golden mag (light or heavy) is not reloading by itself when you change weapon if the CAR has no bullets in the mag, and I also do the same test just with the R-99 just to confirm that when the mag is empty, it will reload by itself and in the case of the R-99, it did reload. It's just the CAR the one that is not reloading and making the "special function" of a golden mag.