Thank you for the quote. It does not say like any other text I have read upon what happen in the barrel. All the tests were done upon the effect of cannister. Why was Grape-Shot not used in Bronze cannon? Iron balls would do a considerable damage to the bore of the gun.
Straith (1836: II-30) states "The cannister has an iron or wooden bottom placed next to the cartidge; an iron bottom bears the explosion the best and causes it to act equally in propelling the small balls; whereas a wooden bottom being immediately torn to pieces, the small balls begin to scatter sooner and are not so effective in their range." The objection towards the iron bottoms was the damage to the bore. It is interesting that British Canister before 1861 was supposed to have wooden bottoms yet Spearman (1828) gives both types.
There is not explanation as to what happens to cannister in the tube but the effect in De Scheel (1777) or in the translation of 1800. Also careful reading of Hughes (1969: 52-3), McConnell (1988: 319), that cannister burst at the muzzle. Now this refers to British Cannister with wooden bottoms. I have most of the contemporary manuals or copies of and I have yet to see an explanation as to what happens in the gun tube. All the tests and results are upon the effect. Alas I have not seen slow motion capture of firing contemporary cannister to explain what exactly happens.
Now your references being both in the 1860s may well be discussing a different construction of cannister for iron guns as that was universally all that the US could cast. Very few Bronze guns were in US service cast in America.
Now can we please consider the forces upon the cannister. A wooden bottom would disintegrate so the gases would be able to exert forces upon the contents and so the lid would be forced open in the gun tube. A metal bottom would deform and not act in the same way. There is not one explanation as to cannister, it is upon the construction of the cannister. I would like to see proper tests upon construction and firing taken place to look into this.
All we can agree is that cannister was rather hit and miss as to its effectiveness and was not the totally devastating man killer of legend on all occassions. Many countries and theorists stated that shot should be used even at close range. The tables given from Adye and Straith in a previous post give some indication upon this.
The British used cannister different from most of the continentals due to experience in America. It was for very close range due to the construction of the cannister with a wooden bottom. It was a refinement of hail shot.
There is still much to learn upon ballistics and especially gun-powder that application of science and considerations can give rather than quoting texts that do not show the point that was being made.