The brass with the thickest case head maintained the tightest primer pockets and had the least amount of change to the flash hole diameter. Vickers hardness testing showed no difference in hardness in the case heads of the Lapua and Norma 22PPC yet Lapua's primer pocket diameter grew to .174 well before the Norma 22PPC which suggests that Vickers hardness made minimal to no contribution in primer pocket diameter changes whereas case head thickness differences was significantly different between the two (i.e., Lapua ~.163.167 vs Norma 22PPC ~..175.178). This suggests that case head thickness may be a strong determinant in the structural integrity of the primer pocket diameter. Also, given that flash hole diameter shrinkage was associated with the brass brands (i.e., Starline and Lapua) that showed the earliest increase to a looser primer pocket diameter, shrinkage of the flash hole diameter may be a major indicator of existing or future loosening of the primer pocket.