Research results on shock unit improvement for visual study of nonstationary gas flow in cave of firing sound reduction device (FSRD) and its efficiency determination are given. An approach of experiment arrangement and procedure on two-dimensional and axialsymmetric model is considered. Operability of the unit that could stand test increased loadings and its maintenance workability are shown. Verification of results obtained from the shock unit by its comparison with results obtained in repair determination of FSRD examined under proving-ground tests in a fire-arm is carried out.