This report addresses the performance testing of four 5” Hamamatsu R1584 PMTs which are to be used in the Heavy Gas Cherenkov Detector for Hall C at Jefferson Lab. Two older Burle 8854 PMTs are also tested as a comparison. The gains of these PMTs are measured at various voltages using two different techniques, and the resolution of the PMTs is briefly investigated. The gains of the Hamamatsu PMTs are found to range from approximately 2.6-8.7 ×107 at the nominal voltage of 2000V. This is above the manufacturer’s specification of 1.4 × 107 . The Hamamatsu and Burle PMTs are all found to have similar resolution, with the Burle PMTs having slightly higher.