Chapter 40: Chapter 40 A spot of Mechanics

Poppy frowned at the spot where, until moments ago, a small pile of prototype black powder had rested. The green orc reached up and scratched his thinning hair. “Huh. I expected more boom.”

Nathan stepped up next to the alchemist. “Yeah, it’s not quite done yet. If you mix it even finer that’ll help. The other thing that needs to happen is to grain it, so you have tiny little pellets instead of a fine powder. The way you do that is to mix in a little bit of water. The goal is more of a putty than a slurry. Then you rub it through a mesh screen or squish it into cakes and crumble them. You might need to heat it a bit to dry it out.” He gestured at the metal sheet. “Carefully, of course. You want little grains of a consistent size that are all three components integrated nicely. I think the correct size for the biggest explosion is small, but not so small you’re all the way back to powder.”

Poppy pursed his lips. “Why does making it in grains help it explode? Seems like you would fit less material in the same space if it’s not a powder.”

“The saltpeter dissolves a bit in water, so I think it helps mix all the components even more finely and keep them from separating. Having them in grains means there’s a little bit of space between them, like you said. Because the grains have some space between them, the heat and explosion can propagate faster.” Poppy was still giving him a dubious look, so Nathan elaborated further.

“Say this is one grain of powder.” Nathan marked a circle on the board. “And there are a few others piled around it.” Nathan drew another three circles to the right of the first shape, making a diamond of circles where they each touched two others along the edge. Then he tapped the chalk on the leftmost circle. “When this one burns, the hot air and heat can pass through the gaps between the grains, lighting other grains farther away than if it was all just a mess of solid powder.” He drew a line directly from the left circle to the right circle, across the gap in the middle of the diamond. “So when a fire starts at one side of a pile of powder it gets to the other side faster, and you get a boom instead of a woosh.”

Poppy nodded, agreeable. “You’re good at explaining these things. Have you done some teaching?”

Nathan snorted. “Yeah, a little bit. Not on how to make explosives though, that would have been much more fun. Now, about that primer mix…”

Beatred had been lurking against the back wall, but now she spoke up. “So we can make the explosives, and I expect Poppy will need to experiment with them. What about me? I can tell you that I’m not going to make one of these right the first time off.” She gestured to the large slate, where Nathan’s crude diagram of bullet mechanics still rested.

Nathan nodded, turning back. “Right. Yeah, we can talk about the primer later. Though if we can't solve it, I bet we can just use a simple heat enchantment.” He pointed at the metal rod that Poppy had used to light the gunpowder. “Before we can really get going on making the guns we need to test stuff out. Do some experiments, and that will require some prototypes.

“We probably want to start with just a simple barrel that needs to be loaded by hand with just some loose powder and a small ball of lead to act as a bullet. Light the powder with a small hole and then you can start getting a sense of how much powder is right, and how tightly the bullet needs to fit the barrel. That sort of thing. Get the exact ratios of bullet weight to powder weight to barrel size nailed down first.

“I think you guys will need to work together a fair amount to make sure you’re not going down the wrong path. You need to figure out the details of the casing and bullet before you can really start going on gun design.” Nathan laid out a few more suggestions for a scientific approach to figuring out the right numbers.

Then he turned back to the slate, picking up the chalk again. “I think we should aim for two different designs of gun and cartridge. The first uses a cylindrical cartridge, where the cartridge is the same diameter as the bullet all the way back. This will go in a short-barreled handgun, meant to be used to shoot a lot at close range. Smaller barrel, less powder, lower power. There’s a few ways to design it, but the one that we’re most likely to use is a simple revolver.” Nathan was sketching out a classic old-west style revolver as he talked, including the trigger guard, handle and hammer.

“The trick here is that there’s this central cylinder which can hold multiple bullets. Between six and nine, usually. There's one barrel, but when you fire it automatically rotates so that the next cartridge is in line with the barrel. The internal mechanism is kind of tricky, since what actually shoots the bullet is this hammer coming down on the back of the bullet. Either it’s got a pin that hits the primer, or we just seal it with thin paper and the pin is enchanted. But you want it to fire when you pull this trigger here, which requires a sort of catch and lever thing here, with a spring somewhere in the handle that pulls it back into place after the shot…”

Nathan looked back from his increasingly detailed drawing to see Beatred watching intently, fascinated. Poppy was looking a little boggled.

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Beatred stepped forward, taking the chalk from Nathan. “It looks like you’d have gaps in your barrel here and here, where the cylinder lines up with the barrel and where the hammer goes into the barrel. Wouldn’t that explode your hand? And how does the cylinder rotate automatically?”

Nathan shrugged, pointing. “That’s why it’s lower power. It doesn’t need to be perfect, just close. And the hammer needs to be heavy and the pin small so it doesn’t get blown back. I think you put something like a gear on the back of the cylinder, then you stick a piece on the lever attached to the trigger so that pulling the trigger automatically rotates the next cartridge into place.”

Beatred was nodding. “Looks tricky. The sort of fine work that you don’t get to do very often on weapons. But critical to this thing working. I love it. Ok. You mentioned two designs. This one looks fascinating, what’s the other one?” She handed him back the chalk.

Nathan had to stoop low to access a clear space on the board. “It’s called a rifle. Meant for long-range accurate shooting. Long barrel, lots of powder, strong explosion. You make a tapered cartridge where the bullet is smaller than the body of the cartridge, so you can fit more powder in and make your bullet go faster. It also means that there’s less air resistance on the bullet so it’ll fly farther.” Nathan sketched out the cartridge, showing where the casing widened out to hold more powder. It looked like Poppy wanted to ask a question when Nathan mentioned 'air resistance' but he held himself back to let Nathan keep explaining.

“Because you have more powder, you need a stronger chamber. The design we’ll almost certainly use is called a bolt action, where you put a cartridge into an opening, then push this lever forward. The bolt, here, moves the bullet into the chamber. Then the lever rotates down a quarter turn and the bolt screws into the back of the chamber, forming a really good seal. The firing mechanism just pops the pin through the bolt and into the back of the bullet, though making it able to deal with the bolt movement can be tricky. You can either feed cartridges in by hand, or you can make magazines that go in the bottom. They’ve got a spring in them that pushes cartridges up into the gun. So to reload you just turn the bolt a quarter turn, pull it back, replace the cartridge, then push it forward and screw it back in. You can make a magazine setup where a spring pushes a new cartridge in from underneath.”

Beatred looked enlightened. “It screws into the back of the chamber to form a seal, that’s elegant! How do you clear the casing after the cartridge goes off? It needs to be gone, yes?”

“I’m not sure about this one, but I think you put a little lever here that engages when you pull the bolt back. It just flicks the casing out sideways. I can get you a better answer later.”

Beatred didn’t mind, just looking over the diagram with a hungry gleam in her eyes. “Why does the back look like this? I notice you don’t have a handle on it.”

“Oh, because the cartridge is bigger and shoots the bullet harder there’s a lot of recoil, or pushback from the gun firing. You brace this part against your shoulder.” Nathan looked around the room and grabbed a broom. He aimed it at Poppy, who was watching with an amused look on his face. “See, so when the gun fires and jerks in your hand, it’s braced against your shoulder.” Nathan jerked the broom to simulate recoil.

Then he paused and took a breath, halting the frantic torrent of words. He looked over the diagrams, trying to think of important details he’d forgotten. There were a hundred important details he hadn’t gotten to yet, but this would be enough to get started. Oh!

“One more thing for now. The bullet itself is made of lead. It’s softer than the steel of the barrel, so it’ll engage with the groves to spin properly without messing them up. It’s also easier to make a bunch of lead bullets, for reloading empty cartridges.”

Beatred was nodding along, pursing her lips as she thought about Nathan’s point.

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