From Guns.com:

The bullet is flanged with four fins for straight flight, like a dart, which are encased in a plastic sabot that falls off as soon as the bullet leaves its smooth-bore barrel.  The bullet has internal electromagnetic actuators that correct its flight; it doesn’t need to spin, it stabilizes itself.  “The natural body frequency of this bullet is about 30 hertz, so we can make corrections 30 times per second. That means we can overcorrect, so we don’t have to be as precise each time,” Jones said.