You can store stacks of single STANAG ammo in you inventory differently. But the highest stack comes from an emptied 60 rounds magazine (double-clip)
There should be a default stack which can´t be increased by filling and emptying the biggest magazine.
If you find single ammo bullets you can stack them up to 30 I think and split them to 15.
But if you find a 60 round mag you should only empty it to 2x30 rounds
For a 40 round mag 1x10 and 1x30
And so on. {F28969}