JC, you're WAY on the safe side with that gun and 67MM CIP loads.
Miller, I think you need to reread Thomas. I can't find any quote from him about the whole discussion "starting" in the 60's. In fact, he says: "I should have thought that all these doubts and misunderstandings had been cleared up by now, but this is evidently not the case . . . " And although the Thomas article in question dates from 1964, the test he conducted with Eley shells goes back "some years ago". Also, as far as I know, he's the first one to show actual pressure and velocity figures. Burrard certainly said that the shells were safe, but he did not provide the results of a test, as Thomas did.
What Thomas is doing in his article is not disputing what Burrard found, but rather correcting the conclusions of people who misread Burrard. Both Thomas and Burrard point out that you don't want to grab just any 2 3/4" shell and fire it in a gun with 2 1/2" chambers.
Bell makes a significant contribution to the discussion by dealing not only with factory shells loaded to CIP pressure standards, but by testing various reloads as well. In addition, he also tests the effects of lengthened forcing cones on pressure, concluding that there is usually some reduction in pressure with the longer cones.
