Hard Maths: Content Posts

[hal]

Originally Posted by clu2415

I was looking into deriving bullet mass and velocity for the UT guns but the problem is that the UT guns were designed around dice of damage instead of physics. For instance, 10mmCLR is in theory comparable to the modern day .416 Barrett or .408 CheyTac calibers, but those round lob bullets that weigh more than the entire 10mmCLR cartridge. My gripe was that pistols, assault rifles, and sniper rifles all deal the same damage with explosive or shaped charge warheads just because the bullets are the same diameter.

In thinking about deriving bullet masses and the like, it occurs to me to wonder...

10mm would be the diameter, and if the bullet is built like most boat tail bullets, its length to width ratio would be what, roughly 3:1? If you know the material the bullet is made of, and you have the rough dimensions, you should be able to get the mass of bullet. Then, using the formula - derive the velocity based on the bullet mass being a known quantity and the damage value being a known quantity.

Something for me to work on tomorrow night perhaps.

[thecommabandit]

All's been quiet over the holidays, as I was visiting family and enjoying all the cheese. Now it's the new year and there'll be two new posts by Thursday, so stay tuned.

In related news, I recently overhauled the look of the blog. I'd realised it had been on a completely unchanged default look since I made it and I wanted something more unique. I've made some changes so please give me some feedback on whether you think it's better, worse, about the same or whatever! Especially on text -- one of the earlier comments someone left was that the text was hard to read. I've since changed the font and increased the text sizes, but let me know if it still persists.

[thecommabandit]

And the first post of the new year is a rehash of old content-- I mean a callback! A reboot! In all seriousness, this post is another on redpowder and prismatic weapons, but this time focusing more tightly on the equipment itself. There's premade statistics for prismatic muskets, pistols and blinding bombs, as well as new rules and options for redpowder and prismatic arms.

[Kalzazz]

This is very awesome, as it answers the big question 'how much it cost!'

If red powder made it to TL 6, would a red powder cartridge be able to cycle a automatic? Or would it be restricted to revolvers etc?

[thecommabandit]

Originally Posted by Kalzazz

If red powder made it to TL 6, would a red powder cartridge be able to cycle a automatic? Or would it be restricted to revolvers etc?

Tricky question. If I understand correctly, most automatic firearms use gas from the propellant to cycle the action and chamber a new round. Redpowder "cartridges" would be sealed (and aren't "unsealed" by firing, like bullet cartridges) and anyway wouldn't create too much gas. Automatic prismatic guns would probably be restricted to hand-driven gatlings until you can have electrically-driven loading mechanisms (probably TL7?). Though I'd welcome an opinion from someone more informed about firearms than me.

[johndallman]

Most semi-automatic pistols are recoil-operated, rather than gas-operated. However, since you do seem to be using semi-realistic chemistry (if not optics) for redpowder, there are a few problems.

Where does the oxygen for the magnesium burning come from? The easiest way to get it will be to use more saltpetre in the serpentine powder mix, but you need a fair bit: 101 grains to each 24 grains of magnesium. You'll also have 53 grains of left-over potassium and nitrogen, so you will have more gas, and more fouling than you were planning on.

You'll also need a positive breech lock, rather than a strap, given this gas and the very high flame temperature of combusting magnesium (up to 3370K).

[thecommabandit]

Originally Posted by johndallman

Where does the oxygen for the magnesium burning come from? The easiest way to get it will be to use more saltpetre in the serpentine powder mix, but you need a fair bit: 101 grains to each 24 grains of magnesium. You'll also have 53 grains of left-over potassium and nitrogen, so you will have more gas, and more fouling than you were planning on.

The answer to this is "It's Science!". Don't worry so much about the chemistry.

Originally Posted by johndallman

You'll also need a positive breech lock, rather than a strap, given this gas and the very high flame temperature of combusting magnesium (up to 3370K).

I'm afraid I don't know what a positive breech lock is.

[johndallman]

Originally Posted by thecommabandit

The answer to this is "It's Science!". Don't worry so much about the chemistry.

Hey, you introduced magnesium combustion. What you actually mean is "it sounds like science, but don't look at it closely."

Originally Posted by thecommabandit

I'm afraid I don't know what a positive breech lock is.

That means that the gas pressure has to actually break something to escape, and the thing it has to break is far too strong for it to manage that. A leather strap is not up to that: it needs to be interlocking metal parts. This isn't all that hard, because gas pressure never tries to turn anything, it just pushes.

Before we try to figure out the easy way to do that, I notice you said that your redpowder cartridges would be sealed, and would not be unsealed by firing. But laser light has to get out of them. Presumably they have a window made of something transparent?

[thecommabandit]

Originally Posted by johndallman

Hey, you introduced magnesium combustion. What you actually mean is "it sounds like science, but don't look at it closely."

That's a better way of putting it. If we're being scientifically accurate, ruby doesn't lase at a wavelength useful for weapons, magnesium wasn't discovered until 1808 and can't pump a ruby laser, and ruby dust wouldn't burn and would remain in the chamber after every shot. That's what the supescience caret (TL^) is for!

Originally Posted by johndallman

That means that the gas pressure has to actually break something to escape, and the thing it has to break is far too strong for it to manage that. A leather strap is not up to that: it needs to be interlocking metal parts. This isn't all that hard, because gas pressure never tries to turn anything, it just pushes.

Before we try to figure out the easy way to do that, I notice you said that your redpowder cartridges would be sealed, and would not be unsealed by firing. But laser light has to get out of them. Presumably they have a window made of something transparent?

My intention for the leather strap was something akin to a miniature belt -- it's attached by a pin to the body of the weapon, then you wrap it around once or maybe twice and hook it onto another pin. But I did mention metallic clips, I think? The breech fastening would be important in TL4 prismatic guns, since they have "open" chambers, but in prismatic guns that use cartridges, the cartridge itself is the chamber, so providing you've used decent glue, you should be alright.

With regards to how the cartridges are made, that was mentioned in the original post:

Originally Posted by Me, back in February

An even cleverer player will realise that placing the redpowder within a reflective casing can replace the chamber entirely... and possibly invent cartridges made from brass or bronze with a polished interior and a crystal or glass window in the front that locks into place with a similar window in the weapon's breech.

TL6 and later redpowder cartridge would likely look almost exactly like modern real-world firearm cartridges, just with a glass window in place of the bullet.

[thecommabandit]

I'm continuing my tradition of making posts at the last minute for GURPSday with today's post. However, I'm breaking my other traditions with a completely new genre on my blog: superheros! Monica Harmann is an NYU college senior who recently discovered she can run as fast as a speeding car and jump three blocks in one leap. She's designed as a "gritty" or "street-level" superhero. Following some useful feedback from Pseudoboo, I've also added some more "methodology" to this post format, about motivations for build choices.