For a rifle cal 45 to 54, one or two discharges is about what I average. Depends how tight the ball is loaded, how long the barrel is, and caliber, whether the rifle is flint or percussion. I suspect you could probably unload a whole revolver cylinder with just one CO2 cartridge.
And Scott, I can maybe at least tie your 'that stupid' experience. I used a discharger to clear a dry ball from my flinter. After the ball was out, I thought, "Gee, I wonder if there's any gas left?" So, I pointed the discharger down range and squeezed the handle. I launched the flint adapter off the end about 15 yards downrange. I say 'about' 15 yards, because I never did find it to measure the distance precisely.