Abstract: A mortar bedding or training round has a canister filled with a heavy, dispersible filling and a sidewall that will rupture after firing of the round. The canister sleeve may be dimensioned to provide an expansion gap within the barrel, allowing the canister sidewall to partially expand upon firing, weakening it for subsequent rupture upon leaving the mortar barrel. Such a round can bed a mortar without launching a projectile to a high altitude where it might be detected.