This report deals with the problem of measuring the rotation of a projectile spin without altering the center of gravity, exterior surface and true weight of the projectile. Twenty millimeter projectiles were magnetized and fired parallel to a 12 foot long coil. The induced electromotive force e. m.f. was amplified and recorded on magnetic tape for playback through an oscillograph recorder. The period of the generated sine wave was then measured to determine the spin f1T. Different barrels were used to obtain data over a wide range of twists. It was found that this system provided a reliable and production line method for the measurement of spin rate.