A coil/gauss gun is completely different from a railgun. Yes, they both use electricity to fire projectiles, but that's about it. A coilgun uses several coils of wire wrapped around a barrel. Electricity is transferred from the batteries to the capacitors, "charging" them up. A microcontroller then controls the capacitors' discharge and pulses the electricity through the coils, creating an electromagnetic force that pulls the projectile through the barrel and up to speed. The microcontroller is critical; as one coil "fires" it must turn off at just the right time as the next coil comes on. If it's too late, then the first coil might pull the bullet back as the second tries to pull it forward; if it's too soon then the bullet might not go far enough for the second coil to be able to grab it. Though it is far more complex than a railgun, it's still far easier to build a working one (and it'll last more than 1 or 2 shots).
Sorry, but it's an important distinction.