In combination with a cartridge case (10) having a tubular wall (14) and a head (16) closing one end of the wall (14), a primer (20) disposed through the head (16) and a propellant charge (13) in the case (10), a collapsible basewad (12) is disclosed which comprises a unitary body (24) between the charge (13) and the head (16). The unitary body (24) has an upwardly concave upper portion (24) opening to the propellant charge (13) and a generally cylindrical base portion (30). The upper portion (28) is deflectable. These portions (28, 30) and the tubular wall (14) define therebetween an annular cavity (42) rearward of the propellant charge (13). This cavity (42) is collapsed upon ignition of the propellant charge (13) by deflection of the upper portion (28) thereby reducing the recoil felt by the shooter without adding any parasitic weight to the projectile load. The upper portion (28) of the basewad (12) preferably has an inverted truncated hollow cone shape. An upwardly open annular channel (52) in the upper end surface (36) of the base portion (30) of the basewad (12) enhances the sealing force between the base portion (30) of the basewad (12) and the tubular wall (14) of the cartridge casing (10).