Originally Posted By: JayCee
Pete, I would think the highest pressure would be in the chamber, just after the powder ignites, where all the gases are constrained in a small space. As soon as the wad starts moving (and space increasing) pressure should drop rather dramatically.

This is just my logical(?) thinking, ;-)
JC

JC; I do believe you are absolutely & totally corect on this. All I have ever seen correlates this. There have been some pressure curves shown here on the board on several occasions taken from data produced by the Old DuPont powder co back in the early '20's with a variety of powders from fast, slow & Black all loaded to the same nominal ballistics. The point of peak pressure varied by little more than ¼" as I recall & all fell within the chamber of the gun. The reason for establishing the point for recording max pressure in a shotgun's pressure bbl @ 1.0" from breech was that if extended much further it could not be counted on to reliably "always" catch the "Peak" of all loads. The tale told for so many years that Smokeless powders reached their peak pressure some 14" down the bbl in the vicinity of the shooters hand was purely a "Scare" tactic used to discourage the use of damascus bbls. The Gunmakers them selves knew better, with the increased use of smokeless they bagan a gradual "Beefing up" of the guns "Breeches".

Last edited by 2-piper; 09/09/08 09:50 AM.
Miller/TN
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