The nanoscale magnetic properties of frustrated metallic ferromagnets are interpreted by means of a model exploiting the results of combined magnetic and magnetotransport measurement. These frustrated systems are concentrated, homogeneous solid solutions of transition metals in a host diamagnetic metal; the length of magnetic coherence can be very short (assuming values as low as one nanometer) owing to competing magnetic interactions leading to a frustrated arrangement of spins. The isotropic negative magnetoresistance measured in these systems is related to spin-dependent scattering events occurring at a distance of the order of the electron mean free path. Magnetoresistance measurements are exploited to get information on the complex arrangement of spins on this scale length.