A range of small calibre shaped charge copper liners were manufactured experimentally by the electro-deposition technique. The average grain size of the produced copper liners was determined using the SEM technique. The specific breakup time, which represents the velocity difference between the particulated jet neighboring fragments (V-PL), was determined for the range of copper liners of different grain sizes using Zerelli-Armstrong constitutive model. The specific breakup time and the total number of the jet fragments were studied over the range of grain size and the predicted jet temperature.