This started off as a test of a few mini CO2 rocket designs. However, it quickly became a sad failure during testing. I haven't had time to return to this project yet; but, I think a thin film of 3-in-1 oil inside the launcher assembly will allow the ram to slide easier, thereby creating a larger hole in the CO2 cartridge and (hopefully) resulting in a proper launch. The other possibility would be drilling the nail hole slightly larger to install a larger nail.
The assembly and testing video is available at: https://youtu.be/9ERqcfAQA_c
20% for the rockets and >50% for the ram and coupler
Please watch the video for assembly instructions and the results of my testing.