Summary

Simple Cracker for 8g No2 containers. Use small screw in center hole.
After some experimentation, this works well as intended. I suggest a couple wraps of electrical tape around where the top piece ends up on the bottom piece with a cartridge inside to make a better seal. Also, gloves or holding with an oven mitt is wise due to the sub-freezing temp of the gases. Finally, be sure to hold the top on when puncturing the cartridge or the container will rocket out of the part and hurts when it hits fleshy parts of ones face.