Regarding canister, typically you would only have about 5 rounds in the limber box. once the enemy was in canister range, after a few rounds you likely would have either stopped the advance, Were limbering up to run, or had been overrun.
By dumb question, I man one that was not asked… i.e. dictionary definition silent, not spoken.Nice material. One note about canister is that Brother Hunt believed that the canister round prescribed by the Ordnance Dep't for most of the war contained too few projectiles - that may be one reason why he warned that the "tendency" to use canister was "too great". As for dumb questions, I've asked more than my share. (That may be a result of my experience trying to maneuver a replica Light 6 pounder of 18th century British design with its $^^#**& bracket carriage. Not sure how those matrosses could deal with that)
An excellent question that I once tried to research but got nowhere. I do know that in the 18th century the shot in "tin case" (canister) got larger and fewer in number over time. During that period the howitzers were confined as a rule to shell. The US had no true artillery system until 1838, although steps in that direction were taken during the 1820's. The 1841 Ordnance Manual has the dimensions you list.To make the whole canister question more confusing is that the the canister shot in a 12# Field Gun was bigger than the shot in a 12# howitzer. 1.49" vs. 1.08", why? Who knows.
I always like a little light hearted stuff… let me tell you about a civil war projectile.Around Vicksburg 12 pounder and some six pounder case was the most common spherical shell. Some of you might be interested in how case shot was made. It usually had the borman fuse, lead balls being poured into the cavity. The shell was then filled with tar which served as a matrix which held the balls in place. A drill was inserted into the fuse hole and then bored out the tar and lead through the middle. Then the bursting charge was poured into the cavity of the shell and then the boreman fuse was screwed in. This is the typical way a 12 pound case shot was made.
Strangely at Champion Hill several case shells have been found that didn’t contain the regular round case shot but instead had a oblong/bullet shaped projectiles that contained powder. I assume these were firing at batteries in hopes of exploding the limbers. Mistakenly these mini projectiles were thought to be incendiary bullets but they are not. They are incendiary from case shot