Last week I opened a thread about the Hotchkiss-patent projectiles. As my approach is to connect the rifle projectile classifications to the columns in the summaries, I’m going to work, in a sort-of and kind-of way, from left to right:
Again.. sort of left to right. The first two columns are not used very often. These are for seldom reported shot (or, as I prefer, bolt) in 2.6-inch and 3-inch rifle.
But the third column over often has tallies. Note the written adjustment to this column. I think the printed text was “3-inch wrought-shot iron gun, 3-inch bore”. There’s enough redundancy there to confuse any bean-counter. I don’t even want to speculate as to what that column was supposed to have referenced. Instead, since the written amendment of “canister” is clear and consistent, let us settle that the clerks used this column to tally canister, of the Hotchkiss-patent design, for 3-inch rifles. Three more canister columns appear on the far right of the Hotchkiss header:
Note the caliber designations – 6-pdr “Wiard” (2.6-inch bore), 12-pdr “Wiard” (3.67-inch bore), and 6-pdr “James” (3.80-inch bore). The attachment of Wiard and James to those calibers does reflect the cannons produced to those inventors’ designs. But we must also consider the caliber in the generic sense. For instance, 12-pdr “Wiard” was the same bore diameter of a 6-pdr rifled gun (not James, but close…). It is also the same bore diameter used by the 20-pdr Parrott. Also consider, we’ve seen the 2.6-inch caliber columns used to report tallies of small-bore rifle guns such as the Woodruff guns. So apply a grain of salt.
So we have columns. And what made that necessary? Well, Hotchkiss canister were different than other types. Let’s start with a baseline:
From John Gibbon’s Artillerist’s Manual, we have a general diagram of smoothbore canister. In brief, we see the canister with the iron sub-projectiles arranged in order. These would be packed in sawdust or other packing material. The can is attached by rivets to a base, which is augmented by a sabot. Behind that, the bag of powder is “fixed” to allow rapid handling in action.
This form worked well for smoothbore cannon. But in rifled cannon there were problems related to the rifling. First off, with the ignition of the powder, the base needed to expand in order to fill the windage in the rifle for accuracy. But, that expansion should not be “too good” as that would allow the rifling to impart significant spin to the round and thus produce a wild shot pattern. Furthermore, the centrifugal force within the canister could deform the payload – particularly where lead shot was used instead of iron. In a worst case scenario, the deformities might cause the canister to lodge in the bore… and lead to injuries to the gun or crew.
Those were the problems that Benjamin B. Hotchkiss sought to resolve with Patent No. 34,058:
Hotchkiss described the layout of this projectile:
The nature of my invention consists in the employment of an inner case of metal or other suitable material divided longitudinally in one or more places, for the purpose of contributing to the resistance of the case to outside pressure and to inside pressure, while the exterior is supported at certain points in sliding across the grooves of the gun, and thus diminishing the liability of the canister to become bruised or distorted in form, while the strength of the structure opposed to bursting strains is but little if any greater than that due to the outer case alone. This is important because a canister, as ordinarily constructed, is liable to become damaged in transportation, or enlarged at certain points while it is moving across the grooves of the gun, while any increase of strength by simply thickening the case prevents it from bursting with the proper facility after leaving the muzzle of the gun.
The design started with the basic canister form, or tube (“A,” in the diagram), made of tin or other soft metal. In this were arranged the balls (“D”). Hotchkiss canister typically used lead balls. The base (“B”) was attached by nailing or soldering. Though Hotchkiss preferred “to place the tube within a mold and pour therein a quantity of melted soft metal, forming a firm base….” The back (where the powder would attach) was recessed to allow some expansion when fired. This would seal off windage when fired. Hotchkiss suggested the base be “tin-plate” to avoid expanding completely into the grooves.
Furthermore, the recess within the base allowed a powder bag to be fixed and folded. This would avoid having separate powder bags. A fine point we will return to shortly.
Turning back to the tube, Hotchkiss specified a shorter case within, cited as “C” in the diagram. This interior case was …
… divided longitudinally in one or more places, m, so as to allow it to be easily ruptured by a force acting from within outward, while it will resist effectually any exterior strains, or those acting from without inward. This inner case stiffens the canister very materially, so that any ordinary concussions in handling will not bruise the case or change its form, so as to prevent its entering the bore readily. It also aids to prevent the concussion of the explosion from causing the contained balls to wedge the case into the grooves when the gun is rifled, a difficulty which prevents the ordinary canister from being used to advantage in rifled ordnance.
And would that stiffening prevent the canister from expanding?
On my canister leaving the muzzle of the gun, the interior case, C, being divided presents little or no obstacle to the bursting of the case and the liberating of the inclosed balls in the ordinary manner.
Adding to this arrangement, Hotchkiss allowed for a metal plate (“E”) between the tube and base to prevent the soft metal from being deformed by the payload. Likewise a similar metal disk “F” was at the top, with the ends of the tube bent over in the normal manner for canister.
Turning back to the powder bag, Hotchkiss proposed to provide fixed ammunition without using the sabot seen for smoothbore canister. The method employed another metal disk, “G”, fixed by screw “I” to the base. Then the cartridge bag (“H”) could be folded within the base for shipment (Figure 2). When issued for use, the bag was unfolded and filled with powder (Figure 1). “By this means my improved canister has all the facility of transportation and safety of the detached canister.”
Now let us walk through how this canister would be handled by the artillerists. When issued, the canister arrived boxed and without the powder bags filled. The ordnance teams (or cannon crew as the case might be) would unfold the bag and fill with powder. When the right measure is drawn, the end was tied. At that point the round was ready for use, and would find a slot in the ammunition chest.
But, you ask, what about all these tales of “double canister”? Well that would be hard with fixed canister, right? But with Hotchkiss’ pattern canister, that was made easier with the issue of canister without filled bags. Still, that raises a lot of implications, particularly someone thinking ahead for the possible need to fire double canister. One flag I would throw out here – it was possible for the crew to fill the bag at the limber. In other words, they might wait and prepare the round for use right there under fire. But how would you, battery commander, prefer? Certainly a lot of “place and time” particulars that might be applied.
At any rate, we can see from the patent information the Hotchkiss canisters deserved to be tracked on a separate set of columns from other canister designs.