Jason Rollette Railgun Blog, building a home made railgun. Miniature magnetic gun (rail gun) NEW Rail Gun! The magnetic field produced by the rails can be estimated by the Biot-Savart Law, which calculates the field of a current carrying long straight wire; B = u0I/2pir.
The plot on the right shows how the magnetic field around a wire rises linearly with current. The wire in this case has a radius of 0.00635m and its length is dimensionless. Notice how one Tesla is not achieved until 35000amperes flow through the wire: Producing a strong field in a straight wire requires vast amounts of current, and there are several more efficient ways to achieve these high field strength values without resorting to several tens of thousands of amperes. Some of these methods are to be explored in another, future Railgun design.