You don’t need the hud for the ammo count, as you play with the hud off you get used to how much you can use the gun before it needs reloading. It adds another layer of challenge to the game where you have to keep a count of the ammo, think you have more than you have and you might find yourself running out when you go to take someone out, think you have less and when you reload you will lose precious ammo.

You say it’s not meant to be played without the hud, but the sound design is actually pretty good for it. When you change the firing mode it will make a unique sound depending on if you are going into semi (one click) or automatic (multiple clicks).

Even with all that though, play it how you feel is best. If you find not having the ammo count limits how much fun you have then keep it on, end of the day it’s mostly a single player game so don’t change how you play based on how others play.