Originally Posted by True_Minecrafter
I think what the picture intends to happen is that since the Cartridge is sticking out a bit, when you drop the shell inside it will push the cartridge up into the puncturing device thing, then it will push the ball out and I will remove the cartridge.
This isn't minecraft.
The escaping gas will take the path of least resistance.
Your could just get some stomp rockets from Toys R Us and shoot farther.