When you have multiple coupled mags in your inventory it will only reload the highest mag in your inventory. This seems to be the same issue when you have multiple canteens in your inventory when you go to fill them. I have no been able to test with multiple version of other mags. Perhaps if you have multiple Magpul mags for example the same issue would occur.
- Legacy ID
1: Join server with same version
2: Have multiple mags in your inventory
3: Hit F to reload a new mag into your inventory
4: Hit F again to reload a different mag, if you have multiple coupled mags it only displays the one
Youtube video with issue
If you have multiples of the same mag, it will only load the one with the highest amount of ammo. It will not cycle through the mags, this is a feature of the arma engine. With multiple canteens, you have to select each one into your hands to refill them.
The mag acted on when you press reload will be the mag that is top left of any other mags in your inventory. Simply move the mag you want to reload so that is is in an inventory slot up and to the left of any others.
If your use your scroll wheel before hitting F it will give you other opions of things you can do... like choosing a different Mag to use when you reload. I bound my mouse scroll up and down to my keyboard since my scroll wheel doesn't work. I've never had an issue trying to reload mags. As far as the canteens go, what are you looking for a 1 button press to auto refill all your canteens? This game is going for some level of realism, hence having to put each canteen / water-bottle in your hand to refill.