This mod lets you create a keybind in the settings to check how much ammo is left in the magazine. At the same time it hides the default ammo counter on the bottom right.
Download the release you want (v2.0+ for the Anomaly Magazines version, v1.5 for the independent one).
Unzip the folder and drag the gamedata folder into your your stalker folder.
Open the ingame control settings and set the Ammo Check button to whatever you want.
If you use the Ammo Type Check 2 keybinds-Edition you can also find the button config there.