The levitation and pinning force properties of nanocrystalline MgB2 superconductors prepared by a mechanical alloying technique with varying milling duration have been investigated. Levitation force measurements under zero-field-cooled regime were carried out at different temperatures (16, 25 and 30 K) as a function of the gap between bottom surface of the superconductor and the top surface of a cylindrical Nd-Fe-B permanent magnet whose diameter and height are 30 mm. An increase in the levit...