Don . . . "increasing velocity requires reducing pressure". Are you speaking in general, or only in the specific case of the changes that take place as a shot column passes through the choke? The specific case of a fluid passing through a constriction. I ask because, while pressure and velocity are not directly related, more often than not an increase in velocity will be accompanied by an increase in pressure. Or at least that's what you see if you look at a reloading manual. Good point. However, we need to look at several "pressures." I agree that there is not a general relation between peak breech pressure and MV. However, there is a very direct relationship between average barrel pressure and MV. For example, a fast powder can produce a higher breech pressure and a lower average barrel pressure than a slower powder; this is because the charge of slower powder contains more chemical energy - the retarded burn rate allows a larger charge of slow powder without high breech pressure. By the time the shot reaches the choke, the powder is long since burned out and the choke passage is a typical fluid dynamics event. IMO
