Miller, I know you don't care much for Thomas. But to give him his due, I think you need to reread what he wrote. Concerning Burrard, here is what he had to say. Note that he clearly gives Burrard credit--making clear reference to the longer shells containing a heavier load:
"Burrard leaves no doubt in his readers' minds that the danger in question arises from the inability of the longer case to open up properly in the shorter chamber, and the higher pressure generated by the constriction thus formed. IT CANNOT BE TOO STRONGLY EMPHASIZED THAT IT IS INDEED DANGEROUS, IN GENERAL, TO USE CARTRIDGES WHOSE UNLOADED CASE-LENGTH EXCEEDS THAT OF THE CHAMBERS OF THE GUN."
"But in the particular case cited by Burrard, the main danger arises, not from the constriction when the cartridge is fired, but from the fact that the longer-cased cartridges he had in mind invariably carried heavier loads; and heavier loads in a given gun, USING A GIVEN POWDER, of necessity involve higher pressures. It is, in fact, pressure that causes the danger."
(Emphasis Thomas.)
For those who remained concerned (for whatever reason) about the danger of British shotshells loaded in 2 3/4" hulls but designed for guns with 2 1/2" chambers, Thomas then goes on to publish the Eley test results, which show scarcely any variation in either pressure or velocity, whether the shells were fired in a barrel with 2 1/2" or 2 3/4" chambers.
