AbstractDuring jet formation and elongation, the shaped charge linear material is subject to forces which vary extremely in both magnitude and direction. As a result, the direction in which the slip planes are formed in the material, changes so as to comply with the force direction and strength. By following the direction of the slip planes from the beginning of liner motion until the jet breaks up, it is possible to suggest a description of the internal changes occurring in the material during liner collapse, jet formation, and jet elongation. The mechanism obtained by this study may account for the slight systematical deviation by a jet from the original shaped charge axis of symmetry, such as has been measured very accurately using the orthogonal synchro‐streak technique (OSST) developed by Held. The mechanism may also explain some jet details observed in OSST photographs and flash radiographs. The modeled mechanism identifies the possibility that some basic differences may exist between the break‐up process occurring in expanding rings and shells and the break‐up process occurring in shaped charge