get in slammer up as commander, execute
vehicle player setMagazineTurretAmmo ["500Rnd_127x99_mag_Tracer_Red", 1, [0,0]];
hint str (vehicle player magazineTurretAmmo ["500Rnd_127x99_mag_Tracer_Red",[0,0]]);
ammo count shows 1 and so is hint
fire away and reload
execute
hint str (vehicle player magazineTurretAmmo ["500Rnd_127x99_mag_Tracer_Red",[0,0]]);
it shows 0, however the loaded mag is full, it still shows ammo for used mag.
execute
vehicle player setMagazineTurretAmmo ["500Rnd_127x99_mag_Tracer_Red", 1, [0,0]];
hint str (vehicle player magazineTurretAmmo ["500Rnd_127x99_mag_Tracer_Red",[0,0]]);
the loaded mag is still full but hint shows 1, which means it set ammo on 3rd mag not on 2nd.