I don't think anyone has done any tests to find out the impact on the velocity of the charge at the INSTANT it enters the larger bore, but most certainly they have done tests to determine the impact on the velocity at the muzzle. Their initial tests showed an actual slight INCREASE in muzzle velocity with a particular load that was fired in a sub-gauge reducer/larger bore barrel combination vs. being fired in a nominal gauge barrel. They were uncomfortable with the data they collected because it was, as you indicate, counter-intuitive, thus their decision to hire Bell to confirm or nullify their data. His tests showed the same resulting slight increase (or at some times no change) in muzzle velocity. While it would SEEM logical that a 12 ga. wad would not be an efficient seal in a 10 ga. bore, the only data available at this time indicates this isn't the case. I asked if they had a theory as to how you could get even a slight increase in velocity, and they did, but my memory is a little unclear on what they said - suffice to say I was a little doubtful of their idea although I certainly don't have a better explanation. It had something to do with a decrease in total friction of the shot column against the bore as the shape of the column expanded and shortened upon entering the larger bore (if I remember correctly).
Last edited by vh20; 10/13/09 01:27 PM.
