The invention relates to an arrangement for supporting a shell (1), such as a mortar shell, into the barrel of a breech-loading weapon, the arrangement comprising a support element (8) to be fastened to the tail of the mortar shell, the element comprising a rim flange (87), means for fastening the support element to the tail of the mortar shell (1), and firing means (9) for firing an actual primer (5) of the mortar shell (1) for firing the mortar shell. The arrangement is characterized in that the means for fastening the support element to the shell tail are arranged in the support element (8) by means of finger-like fastening members (80) settling onto the shell tail tube (3) and arranged to constitute an interference fit between the shell (1) and the support element (8) when the shell (1) is placed in the support element (8). The invention also relates to a support element and a method for supporting a mortar shell (1) into the barrel of a breechloading weapon.