In trying to learn when burn-out occurs relative to peak pressure, I've gone through the limited materials readily available here. The best reference at the local library is Corner's book. This was written in the UK just after the war to summarize the state of the art with regards to theoretical calculations. Digital calculations of the formulas used was just beginning and not greatly covered; at that time "computer" was generally a person's title, not a machine.
Results of simplified burning models were poor. These assumed burn-out occured near peak pressure, and they showed the fast fall off in pressure I've been noting, which does not match the rounded fall off his piezo data shows. Interesting are his comments on how burning in guns differs from that in pressure vessels due to erosive effects on the charge of the gas flow.
As the math models become more involved, the theoretical calculations begin to better match piezo data and the burn-out moves to after peak pressure. Confounding their calculations was the engraving of the projectiles into the barrel, a problem which confounds the calculations in sporting rifles to this day. Of note was that burn-out could in principle occur after the muzzle.
While quite interesting, Corner's work does not answer the question I raised. Corner was concerned with "guns" which are cannons and howitzers. He favorite example was a hefty AA gun. The propellants were not progressive; the engraving forces were relatively small; the loading densities were lower than in sporting rifles; and the chamber volumes were huge compared to the bore cross section.
It'll be months before I can get some time at the big engineering library down the road. I remember there is a book there by Krier with a section on the simulation of small arms circa 1970, and perhaps some answers might be found there. I do recall that bullet engraving was a problem on the models, but perhaps there will be some relevant experimental results.
Karl
