I'll explain these mortars. They consist of a a film canister/fin assembly secured to the cap of a pop bottle(not 1 or 2L). The pop bottle is filled with kitty liter or other light material like ground up corncob. The bottles are scored so they will burst apart on impact. A charge of black powder(approx. 1/4 tsp) is placed in some saran wrap with a piece of cannon fuse then tied in a small ball with the fuse sticking out. This charge is placed in the film canister with the end of the fuses pokeing out of a hole in the canister lid. You light the fuse then drop down the mortar tube. The blackpowder explodes blowing the cap of the film canister shooting the mortar round out of the mortar tube.