The Sparks shot towere built in 1808 that gave a 150 foot drop was said to have supplied ball for the war of 1812. Bishop a co owner had to sell out his interests because he was a Quaker and did not believe in manufacturing war goods.
What fascinates me the most about these towers is not the fact that they made shot shell shot but the amount of production in general. One tower sold over 400,000 25 pound bags of shot to the US Government a year. Each could put out at least 2 ton a day. The market was much larger than I had thought.
My original ideas about colonial shooting was that they bought a rifle, a mold was made with the rifle, and they casted what was needed. Looking at the figures for output on the shot towers and the fact that the British and French were exporting shot and ball to the country before this time I am speculating that shooters liked to purchase as close to a "box of ammo" as they could. There is more than one thing leading to this speculation. I am sure a fair amount of shot and ball was exported for the fur trade to the Indians. It makes a great deal of sense to me that they would buy ready made shot and ball. The NW Trade Gun remained basically a 24 gauge for at least 70 years. While there are many explanations for this, a uniformity of ammunition availability could play in.
We have all seen these small bag molds that no modern caster really wants to use and carries more for decor, because they are a real PITA to use produce any amount of ball. They make a lot of sense if carried as a supplement to the supply. It was stated that they would resuse ball dug out of game. For casting a very few ball by a campfire, they make sense. Looking at original rifles, one does notice a commonality in caliber selections. Be fun to have the KRA look into this.
Ball molds of the time were not nearly as convenient as we have today. There were claims of some being made out of wood even. I doubt if the machining tolerances, especially in the Revolutionary times could produce molds within .001 round as done today.
As stated a desire to purchase ready to shoot ammunition may have been a very central factor. It was stated that the Sparks tower was built because Sparks and Bishop got tired of paying high prices for hunting shot and built the tower. Jefferson's embargo also played in. Most people today and back to the start of the cartridge era bought loaded ammo. Handloaders were of course people like the buffalo hunters, but typical rifle and pistol owners bought loaded ammo.
Almost all reference to guns was by gauge. Did they sell ball by count to get a pound? IE 24 ball to equal a pound for the tradegun? At the reenactment Fort William in Thunder Bay, they had a bin of musket balls on display as an example of sale items.
A lot of shooters likely did cast their own, and there are references to the homemade shot for shotguns, but there must have been a very large market for ready to load ball and shot. French and British imports would have been very costly, and it seems the shot towers made ball and shot more affordable.
DP
The air draft systems were invented in 1849 as a means to eliminate the need for higher towers, but I think it was to try to make them under the 150 feet. Another interesting aside is that some used other means for gaining heights like mine shafts.