I have confirmed on different vehicles but my setup I am using is a M-173 (APC).

I have a GE Vindicator Minigun with an weapon modification Additional Clip.
Here I notice it allow me to load a 250 rounds now that I added that Additional Clip option.
I can use 50 round clip or a 250 belt? with it.
I can load a 250 belt twice just fine when I add the Additional Clip when it is a weapon under the street gear > weapons section.

I am trying to use the Ammo bin option to on the vehicle,
When I move the weapon to the weapon mount on the APC, a (Normal, External, Turrent, Remote), it only allows me to 50 clip only.
The reload screen flashes and does not display the reload screen while weapon is mounted.
I can see the reload screen on the street gear > weapons section.

I tried with a GE Vindicator Minigun without an weapon modification Additional Clip also. No Joy.
I even tried to remove the Additional Clip and even the Ammo bin, Nada.
I still see I can load a 250 rounds after removing the items under the street gear > weapons section.

I am out of ideas.

Plus, if it is possible, can we get a unload weapon ammo option too!

If this is about the Chummer program, you'll need to post any bugs about it in this thread here.

Sorry, was following these instructions.

Closer than some I've seen. At least it was in the right folder, but the thread I linked is more likely to draw Nebular's attention & it's where our continued discussion on his creation is.

...while ignoring the big fat Chummer thread you already posted in before your started posting across the boards...