The p per reports an investigation if low temperature brittlement of gun steels of Cr-Mo-V system compared with gun steel 37CrN13MoV by means of Charpy impact test with osillograph to display and record the deformation course of the steel. The results show that the ductile-brittle transition temperature obtained by the decreasing of crack spread energy of the steel accompanying tempe ature to a critical lowest value can truely show that the steel has reached brittle condition. To determine low temperature b...