The paper carries out research into elastoplastic unloading using methods of plasticity theory and solids mechanics. Residual stresses are calculated in a heavy-walled tube made from a dispersion-hardened copper alloy. The influence of the size of strengthening particles on residual stresses in the tube walls is determined herein. It is shown that with the increasing particle size, radial stresses in the former plastic and the adjacent elastic areas increase, whereas they decrease near the outer wall. The growth in the particle size leads to the reduction in absolute values of residual tangential and axial stresses which are one order of magnitude higher than that of residual radial stresses.