Calcualating muzzle pressure from peak chamber pressure would not work as there is additional powder burn (gas generation) after peak pressure is reached, I'd expect. If you had a big enough computer and knew enough of the powder characteristics, you could calculate it. I don't know any practical calculation from what is available.
The pressure is quite low, I'd guess more on the order of 50-200 psi - Greener is reported as turning a section of a barrel at the muzzle to near "foil" thickness and firing without a burst. Further, he is reported to have removed the thin section with a pen knife after the demonstration.
I would expect a strain gage set-up to work just fine. IMO, the shot doesn't "hit the choke." Shot is acting as at minimum a semi-fluid and "flows" through the choke. I expect the shot column has an internal pressure that is a very near reflection of the gas pressure behind it and it is subject to pressure reduction and velocity increase in a constricted passage (venturi effect) such as the choke. Note that a constriction such as the forcing cones or chokes is not to be confused with a restriction/obstruction such as a foreign object inside the barrels. I'd expect a circumferential orientation of a strain gage to yield very accurate pressure within the choke.
This is a subject of considerable interest to me. Let me know if you want to work on it.
Last edited by Rocketman; 12/04/06 10:21 AM.
