Results of finite element modeling, experimentally validated using copper samples with aluminum markers were analyzed for a deep understanding of the influence of processing temperature and properties of processed materials on the strain distribution in the bulk billet processed by high pressure torsion extrusion (HPTE). Calculations were carried out for pure copper for HPTE regimes with resulting strain in a range between 0.3 and 14.9 at deformation temperatures of 25 and 100°C. It was established that accumulated strain at HPTE can be as high as ~11 even in the center of the billet, which shows the high efficiency of HPTE as a method of severe plastic deformation. A comparison of the calculated strain distributions with experimentally measured ones in copper samples made it possible to reveal the spreading of the deformation zone along the height of the billet, caused by its sliding in the die. It was established that this sliding increases with increasing of deformation temperature and of the value of accumulated strain at HPTE. X-ray tomography was used to visualize the change of the shape of wire markers inserted in the billets prior to HPTE processing. Initially straight wires with round cross section transformed to spiral ribbons with a thickness down to 240 times smaller than the initial wire diameter.