Miller, Burrard says: "The effect of the mouth of the case being held in by the chamber cone is much the same as that of giving the cartridge an exceptionally heavy turnover, and the effect on the pressure will be obvious . . . If the mouth of the cartridge is compressed by being held by the chamber cone, the resistance to the initial movement of the shot charge will be greater and the pressure will be increased."
That's all from the same paragraph in Burrard's book, and nowhere in that paragraph does he say anything about the loaded cartridge being longer than the chamber. We know for a fact that loaded cartridges SHORTER than the length of the chamber can and do extend into the forcing cone, depending on how much shorter they are and how much longer the case is after it opens. And we also know for a fact--thanks to Burrard, Thomas, and Bell--that the longer case opening into the forcing cone does not result in a significant increase in pressure.
Thus, both Burrard and Thomas--if you don't read their entire sections on the subject--can be somewhat ambiguous, until you reach their conclusions, which are the same. In Thomas' para following the one you quote, he also clears up the "unloaded case length" issue, when he says: "It is, in fact, pressure that causes the danger: no gun was ever burst or damaged by a cartridge case . . . " That's the same thing Burrard cleared up when he says: " . . . any increase in pressure doe to the longer cartridge case really does not exist . . ."--then going on to specify that the correct powder and shot charges need to be used (as does Thomas).
Unfortunately, if one reads only part of what either Thomas or Burrard writes, or if they're quoted selectively, one can come to a conclusion that is 180 degrees off from that reached by both of them.
