I was talking to my Japanese History Professor today, he mentioned that muskets and shot were heavily utilized going back before the Meiji Era. I was wondering if the Japanese used shot towers or similar technologies during that time period. He said they used mold casting to produce their shot (which I'm inclined to believe), but shot towers were being utilized across Europe and the United States during this time period, so it is possible that they had access to the technology.
I'm not an expert in 19th century Japan, but to clarify full-sized musket balls and cylindroconical bullets in the west were still being made by casting. Shot towers were used for producing various sized pellets like you would find in a shotgun. Some sporting weapons such as punt guns could fire thousands of pellets with each shot, which meant cheaper methods of mass production were more desirable.