Experimental Railgun

Choose one ferromagnetic object weighing up to 5 pounds. Your arms are raised in front of you brimming with lightning, the object suspended between them. The object spins as it gains an electrical charge and then fires at three times the speed of sound.

The object flies in a straight line up to 120 feet in a direction you choose before falling to the ground, stopping early if it impacts against a solid surface of stone or harder mateiral. If the object would pass through a creatures space, that creature must make a Dexterity saving throw. On a failed save, the object strikes the creature dealing 2d8 piercing damage and 4d6 lightning damage, half as much on a success. 

Charged Shot: Rather than firing immediately, you can hold your fire to build a greater charge for a Charged Shot in hopes of obliterating your target. For the duration of the spell, you can use your action to hold your fire increasing the lightning damage. For every round you hold your fire, Railgun deals 2d6 extra lightning damage.

Misfire: If you lose concentration on Charge Shot because of damage, rather than losing the spell, it fires in a random direction. The DM will determine which direction the Railgun fires by rolling a d8.