During the battle of Ramelle, Ryan and Miller run out of ammunition and throw mortar rounds at the Germans, with spectacular effect. However before they throw them they strike them against the base plate of the broken mortar. Mortar rounds have two charges, one to explode on impact and one to blow the round out of the tube. They are fired by dropping them into the tube- if you hit the end of the mortar round by holding it in your hand and whacking it against something, it would blow your hand off. Also, we have been previously told that the mortar was taken out by an artillery round. Yet the wrecked mortar and its ammo are all conveniently to hand, not blasted all over the place.