Police department took possession of my nicest spud gun in college. They didn't see the humor in drunk kids firing across the river at the abandoned flour mill. Best fuel I found was right guard aerosol deodorant.
I didn't make the over barrel under chamber like the video. Mine were the inline version. I'm not sure if it was from over firing cause it was very well used or I over filled it but I managed to blow one apart in my hands. Stung like hell. Once the sting left I built another. Yup I'm a slow learner. Another time I was playing I launched a tater projectile and almost hit a mud hen about 40 yds out. LMAO! That thing took off so fast it almost left a vapor trail.