The paper presents research on the shock initiation of a melt-cast insensitive explosive composition containing 3-nitro-1,2,4-triazole-5-one (NTO), 2,4,6-trinitrotoluene (TNT), wax, and aluminum powder. The composition was elaborated for steel tubes and initiated with the use of boosters of various configurations. Research systems were made to measure the velocity of detonation wave and to determine the type of response of the composition to shock initiation. A relatively long shock to detonation distances after initiation using the boosters with a steel buffer were found. A method of initiating the composition was indicated to guarantees an immediate achievement of the stationary detonation regime. An attempt was also made to explain the observed processes theoretically. The results obtained can be used in the design of munition filled with melt-cast insensitive explosives.