A blast attenuation device (100, 1100) for a gun tube (10). The blast attenuation device (100, 1100) has a first wall section (102, 1102) which defines a first chamber (104, 1104), which extends from an inlet end (106, 1106) having an inlet aperture (108, 1108) to an outlet end (110, 1100) having an outlet aperture (112, 1112). The blast attenuation device (100, 1100) also has a second wall section (122, 1122) which defines a second chamber (124, 1124), which extends from an inlet end (126, 1126) having an inlet aperture (128, 1128) to an outlet end (130, 1130) having an outlet aperture (132, 1132).