Rocketman, Having read perhaps hundreds of your posts, I knew that you knew better than you originally stated, the working principles of hydraulic pumps. However, if our pump/cylinder system was using a compressible gas instead of an incompressible oil, I don't think it would be considered a "hydraulic" system. The foundation pirincples of force equals area times pressure applies to all fluid systems. Also, my example did not state the obvious that if the pump did not produce sufficient pressure, it will stall and no fluid would move. I also did not state the equally obvious that if our hand pump operator had no arms and could not pump the pump that no fluid would move either. My mistake. I know you understand, but others reading this discussion may not have. Public discussions, such as this, have to provide more background information than a simple two-way discussion. I do agree that something may happen to make the powder burn more efficiently as it expands into the almost instantly larger combustion chamber. Earlier in this thread, I postulated that we might even be seeing a sort of the phenomena that occurs with reduced loads of some powders that produces pressure spikes or even detonation. See the cautions and warnings about reduced loads of WW 296 in the .357 magnum for example. I'm not aware of any detonation issues with shotguns; sure for rifle and pistol low density loads. However, the detonation phenom occurs within the case. That is why I wish we could simplify this discussion and power our wad/shot charge with say 9000 psi of compressed air or CO2. Then we could say with certainty that the pressure would have dropped considerably by the time the wad entered the larger bore diameter. With some slower powders, that may not be true. In any case, despite the toughness of the wad skirt, I am still very skeptical that there would be no blow by going from 28 ga. to 12 ga., or .550" to .729" (I don't know the diameter of an average 28 ga. wad.) I do know that in hydraulics or pneumatics, even where the bore size does not open at all, let alone so dramatically, there is no such thing as a perfect seal. Agreed, but the wad skirt seems to be able to bloom the noted 0.09" in radius and maintain a seal. Why, with what you are claiming, we all should be loading our 12 ga. shells with 28 ga. wads. We would get higher velocity at lower pressure with reduced bore friction. No, I don't agree with that statement. 28 gauge shells may actually preform better in a 12 gauge bore, though. I suppose we could put up several thousand dollars and have some ballistics lab prove that you or I are right or wrong. I not interested in who is right or wrong. I'm interested in what is true. [/quote]
