Some of us are struggling with the mines in Natural Selection. It’s a timing thing. You have to dig around for them. You hit the number 5, then wait a second, then left mouse click to select, then wait a second, then left click to place, then wait 2 seconds, the hit 5 to select, wait a second, and so on.
If you try to select and place them too fast you may think you’ve run out of mines when you haven’t. You will always get four mines when you spawn if you have mines.
Note that we are using the same kind of plugin for grenades and they may work in a similar way.