There is a glitch/exploit that involves duplicating items taken from either the ground or a crate.
- Legacy ID
Place item on ground (or in crate)
Right click item to auto-move to inventory
Left click and drag item immediately after right clicking it
Place duplicated item in any container except where the original went and you'll have 2 of that item.
Note: Easier to do with equippable items (magazine, gun, etc.) as it takes a second longer to move.