The results of comparative tests of the regrinding mill DR-500, the ball mill MShT 2700x3600 and the core mill MS 300x200operation with the regrinding of the sands of copper-pyrite middling’s under the conditions of the Urup mining and processing plant are presented. As a result of the tests, the relative grindability of copper-pyrite middling was established in the grinding regimen DR-500 according to the calculated grade, -0,074 mm = 0,86, and according to the calculated grade.-0.2 mm = 0.90. The hypothesis about the selective mechanism of the material destruction along the planes of the mineral fusion with the vein minerals of the host rock was confirmed. As a result of the comparative tests of the regrinding mill DR-500 and the core mill MS 300x200, the data were obtained for the extraction of copper into the concentrate: the core mill was 85.1%; 2,614 and grinding mill 89,67%; 2.403. The mineralogical study of the polished sections showed that the grains of the useful mineral when grinding in the mill for regrinding DR-500 are larger and better disclosed than when grinding in the rod mill MS 300x200. The comparative tests of the regrinding mill DR-500 and the MSC 2700x3600 mill in the closed cycle with hydrocyclone showed that the most effective circulation load of 207% for the DR-500 mill is achieved with water consumption of 1.46 t / h. In this case, the specific productivity of class, -0.074 mm and the content of this class in the grinding product have the maximum value. It was revealed that in order to obtain more fine grinding of ore in the DR-500 mill it is desirable to use a closed grinding cycle with classifying devices.