This glitch only works if you purchase either the Martial Law pack or the Supernova pack add on. Go to any store, and go through the Shop and purchase one of the free Detonator weapons. The gun always comes with full ammo at the starting maximum (5). You can then launch all the mines, and recover them with the secondary fire. Once the gun has been depleted of ammo, you can then sell it back to the store, and re-buy another fully loaded gun for 0 credits. Doing so will continually add your stock of Detonator Mines which you can then sell back to the store for a profit.