A previous study developed a simplified grinding model (SGM) to gain a solution of batch milling although it included an unspecified function of the particle size x, FR(x). The present study analyzes the properties of the ball mill grindability (BMG) to specify the form of FR(x) and discusses the usefulness of the SGM. The BMG test, the locked-cycle grinding with a batch mill and a sieve classifier, measures the mass rate of the finished product per mill revolution at equilibrium, denoted as Gb. The power laws are exhibited by the data of Gb in relation to each of the classifier cut size xc and the product particle size 80% passing xp80. The theoretical Gb is found to be related to each of xc and xp80 only via the unspecified function FR(x). This implies the form of FR(x) to be the same power law, the validity of which is examined with reported data. Then, the SGM with the specified FR(x) predicts the trends of Gb to vary with the mass fraction oversize 74 μm of the finished product, which are confirmed with reported data. In addition, the BMG data are shown to be available for evaluating the material constants used in the SGM.