Abstract: The barrel comprises a unit (1) for initiating detonation connected to a detonation chamber (2) accommodating a combustion-to-detonation transformation accelerator (3) in the form of a space lattice arranged coaxially inside the chamber (2). The size of each cell (4) of the lattice substantially equals the size of cell of a stationary detonation wave in an explosive mixture of preferred composition. The number of cells (4) of the lattice in cross section of the detonation chamber (2) grows toward an open end of the barrel defining through passages (5) for conveying gas from the unit (1) or initiating detonation to the detonation chamber (2). The peripheral passages (5) of the lattice are arranged at an acute angle (.alpha.) to the axis of the barrel.