The atomic processes associated with the plastic deformation of commercial‐quality sintered iron were investigated. Stress relaxation tests were carried out over the 17–19‐kg mm−2range of initial stress levels at room temperature. The experimental results were analyzed with the deformation kinetics theory discussed in Paper I. The analysis showed that the rate‐controlling mechanism is associated with a system of two consecutive energy barriers. At high stress levels only the first barrier is effective. The corresponding activation volume of ∼ 200 b3, measured in these tests, suggested that the Peierls‐Nabarro mechanism was rate controlling at this level. It is proposed that the second barrier is either the second half of the ``camel‐hump'' Peierls‐Nabarro barrier or the resultant of a series of dragging‐point barriers controlling the spreading of the double kink.