Shell for trench mortars and similar firing systems, which shell includes an effective portion, which can be fired from a barrel by a propellant charge, there being a pressure plate provided between the effective portion and the propellant charge, which pressure plate carries the influence from the propellant charge. To provide effective fire above the ground a support portion is releasably arranged in front of the effective portion in the firing direction. The support portion carries a second propellant charge and in its front end a percussion cap, which, when the shell is fired, is located partly exposed outside the front end of the support portion and initiates the second propellant charge when hitting ground. The second propellant charge is located between the support portion and the effective portion in such a manner, that when the second propellant charge is detonated the effective portion is shot away from the support portion and simultaneously the effective charge of the effective portion is initiated with delay.