The interaction of 2 and 5 nm Frank loops with a moving screw dislocation is studied in Fe-10Ni-20Cr alloy (a model of austenitic 304 and 316 steels) employing the newly developed Fe-Ni-Cr interatomic potential in molecular dynamics simulations. The applied potential ensures full stability of FCC phase and smooth evolution of stacking fault energy (SFE) as a function of chemical composition, fitted to be in a close agreement with the CALPHAD database. A model of Fe-10Ni-20Cr random alloy closely reproduces elastic properties and SFE of 316-type austenitic steels. The results reveal a number of interaction mechanisms depending on loop orientation and ambient temperature. Half of the observed reactions lead to loop unfaulting despite a low SFE of the alloy. The unfaulting reactions are enhanced with temperature and the critical stress for the unfaulting is regularly higher in comparison with the loop shear interaction. By comparing present results with a recent study done in a low SFE Fe-50Ni alloy, we reveal that a magnitude of local variation of SFE is an important factor controlling the formation of dislocation constrictions. In the Fe-50Ni alloy, characterized by strong variations of local SFE, the constrictions are almost never observed so that the loop shear interaction prevails, while absorption is rare. In the Fe-10Ni-20Cr alloy, characterized by small variations of local SFE, the constrictions are regularly formed resulting in frequent loop unfaulting.