Don, If there is a reduction in pressure within the shot column it is just a physical side effect of the forced lengthening of the shot column, emphasis on "forced", because all of it simply cannot get through the constricted area in the same length that it was before entering it. Lower pressure within the shot column does not assume no stress is transmitted to the barrel at the choke area. If indeed there is a lowering of the pressure within that shot column it comes at the expense of great outward force which is the result of the column being forcibly lengthened. What I meant was that I do not believe that shot necessarily SPEEDS UP while passing through the constricted area (choke, venturi). This is what I was taught in physics was meant by "venturi effect", the acceleration of the gas or liquid. I am not entirely dogmatic on this point, however, as I cannot prove it either way. If it has been proven that shot accelerates in a choke, I stand corrrected on that point. Sure, shots flows, but not the same as a gas or liquid, IMO. The shot flowing through my reloader is not under several thousand psi, either. Of course no outward pressure is being exerted as the shot enters the drop tube on a reloader, it is only being acted upon by gravity. It isn't hitting a constriction at 1250 feet per second.
The length of choke taper has been debated and argued for many decades. Many different makers had their beliefs/ideas about this. I have my opinions as well, and opinions are all I claim them to be, not fact. However, if the sharpness of taper has no effect on choke performance, why not just try cutting a .040" X-full choke with a taper length of only .040"? This is an extreme example, just to make a point, because hopefully you don't believe that the stresses on the barrel steel in the radical taper would not be greater than it would if the taper took place over a distance of 3/4 inch, or more.
I did not make my point clearly enough in the earlier post, when I said that I would be interested to know what the constrictions were in the bulged barrels, that I was relating it to the earlier thoughts that possibly the proof houses had begun using steel shot proof loads. I certainly don't think that tight choke alone should cause a sound barrel to fail proof with a lead shot proof load. But you don't really believe that all shot, even that of very hard material, flows through chokes without causing stresses to the choke area, do you? Even steel? I think you know how risky it is to shoot steel shot loads through very tight chokes. I have seen any number of ruined chokes and barrels, at a friend's choke tube business, that were ruined by using steel or harder non-toxics through very tight chokes. The venturi effect may have eventually lowered pressures in those shot columns, but it was at the expense of a barrel and a choke tube.
Stan
