Steve Jackson Games - Site Navigation
Home General Info Follow Us Search Illuminator Store Forums What's New Other Games Ogre GURPS Munchkin Our Games: Home

Go Back   Steve Jackson Games Forums > Roleplaying > GURPS

Reply
 
Thread Tools Display Modes
Old 03-06-2021, 06:29 PM   #1
TerryW
 
Join Date: Mar 2021
Default Plausibility check for mixed TL3/4+2 firearm

I have an idea for a mixed tech level firearm, as part of a time travel scenario. I know there are people on this board with much better knowledge of firearms than myself, so I thought I'd ask for a plausibility check.

The local TL is mixed 3/4. Basically a TL 3 nation (Early 14th Century Japan) next door to a more advanced neighbour. Japan doesn't train TL 4 craftspeople, but can buy their products or recruit craftspeople to work there. So I've tried to limit the technology, particularly the metallurgy, to materials available in late 13th Century East Asia. So no coiled steel springs for firing mechanisms. Instead the firearm uses a caplock mechanism powered by a small crossbow rather than a spring.

As far as I can tell, constructing the firearm would need at least the following specialists: A fireworks manufacturer, a chemist/doctor to help with knowledge of chemistry, a metalworker for the cast iron, and a clockmaker or toymaker.

The cartridge case is made of paper, the propellant is black powder, and I'm still trying to decide on the most likely primer.

The firearm is a breachloader. The breech is on the side, and is basically just a hole in the rear of the barrel where the user puts in the cartridge and pushes it forward into the firing chamber. Then they seal the breach with an iron plug. There might be a small arch of laminated bamboo glued to the back of the breach, to push the plug tight against the firing chamber. With the breach sealed, the user pulls back the bowstring and hooks it over the tooth of the trigger nut. Then they pull back the hammer, which is in front of the crossbow mechanism. When they pull the trigger the crossbow string slaps the hammer down into the firing chamber, detonating the percussion cap.

Playing around with lwcamp's firearms calculator, I built an 18-inch barrel longarm firing quarter-inch minie balls, using TL 3 materials and 3 grams of TL 4 black powder. Damage 7.5 (So about 2d), type pi-0.5 (Been a long time since I played, so I'd have to look up what that means). Acc 1, range 70/900, weight 1.5 lbs, RoF 1, shots 1 (40*), minimum ST 6**, bulk -3, recoil 2, cost $80***, LC 3***.

* IIRC, 40 means how many seconds it takes to reload. But the calculator is for a muzzleloader, not a breachloader.

** This part is important, since the character who would be using this is an athletic (High Health, Very Fit) but very short woman.

*** Cost and LC are largely irrelevant, for a prototype weapon that the authorities don't know about****.

**** Yet.

Thanks in advance.
TerryW is offline   Reply With Quote
Old 03-06-2021, 06:47 PM   #2
Prince Charon
 
Prince Charon's Avatar
 
Join Date: Dec 2012
Default Re: Plausibility check for mixed TL3/4+2 firearm

Quote:
Originally Posted by TerryW View Post
As far as I can tell, constructing the firearm would need at least the following specialists: A fireworks manufacturer, a chemist/doctor to help with knowledge of chemistry, a metalworker for the cast iron, and a clockmaker or toymaker.
A locksmith could replace the clockmaker/toymaker (unless they didn't use metal locks in Japan at the time; I'm not sure). That's why wheellocks/flintlocks/whatever are called 'locks.'
__________________
Warning, I have the Distractible and Imaginative quirks in real life.

"The more corrupt a government, the more it legislates."
-- Tacitus

Five Earths, All in a Row. Updated 12/17/2022: Apocrypha: Bridges out of Time, Part I has been posted.
Prince Charon is offline   Reply With Quote
Old 03-06-2021, 07:46 PM   #3
DaosusLeghki
 
Join Date: Jul 2010
Default Re: Plausibility check for mixed TL3/4+2 firearm

Couple of thoughts on this:

* A minie ball is unnecessary and undesirable in a breech-loader. It's not going to mess anything up so long as the bullet is retained in the paper cartridge until it's fired, but there's no reason to use expanding under-size bullets if they're being loaded from the breech. Going with a plain ball or rounded point would be easier.

* 18 inches is a bit short for a barrel. This falls into "super short carbine" to pistol territory for black powder. That's up to you, of course, I'm just mentioning it. You seem to have taken note of it with the low ACC score.

* Ignition is likely to be a problem. Percussion caps and primers are fairly modern inventions. Perhaps it could be a flintlock or something similar.

* Helical springs are hard to make, but leaf springs have been used in firearm lock-work since there were firearm locks. TL3 is stretching it, perhaps, though. Most firearms used V-springs (essentially a leaf spring bent into a V-shape) because they are more space efficient. You need one good piece of steel for the spring, but only one. The rest of the lock can be made of wrought iron or cast iron.

* Reload time for a breech-loader is likely to be around 20-25 seconds. You'd likely still have to prime a pan if you're not using a percussion cap.


*EDIT* 1.5 lbs is freaky light for a longarm. Modern longarms are considered quite light and handy if they are around 5 lbs.

*EDIT2* You might consider looking at the Ferguson rifle. It's way later than TL3 (being used in the American Revolutionary War at the Battle of Brandywine), but it gives you an idea of what was done. Also, you might look at the way that the Dreyse needle gun and the Chassepot seal the breech. No one really figured out a good way to seal the breech without using metallic cartridges.

Last edited by DaosusLeghki; 03-06-2021 at 07:52 PM.
DaosusLeghki is offline   Reply With Quote
Old 03-06-2021, 08:09 PM   #4
TerryW
 
Join Date: Mar 2021
Default Re: Plausibility check for mixed TL3/4+2 firearm

Quote:
A locksmith could replace the clockmaker/toymaker (unless they didn't use metal locks in Japan at the time; I'm not sure). That's why wheellocks/flintlocks/whatever are called 'locks.'
I might leave the existence of mechanical locks for the GM to check out. It can be a surprise for the character. I've been told more about the planned game than most of the other players, because I can be reliably counted on to either act as though I don't know or, if I do plan things out in advance, make them fun for the other players as well. What, you think I'm going to tell anyone other than the GM that I'm commissioning a boomstick? The other PCs can enjoy the surprise just like the NPCs.

Quote:
18 inches is a bit short for a barrel. This falls into "super short carbine" to pistol territory for black powder. That's up to you, of course, I'm just mentioning it. You seem to have taken note of it with the low ACC score.
I'm recycling a character idea from a 3e campaign I never got to play. Absurbly high Health and fitness, cast-iron stomach, resistant to disease, quick, smart, adaptable, basically God's perfect field soldier... except she's five feet tall. She'd be a terror on the battlefield if the weight of the equipment wouldn't kill her. So I'm keeping the weapon compact to reflect the fact that she has the leverage of a twelve-year old.

I'm not sure about the metallurgy for leaf springs. It might not be good enough for lock mechanisms yet. But I might also throw that in as a false path for the character to chase for a while.

20+ seconds sounds like a good starting estimate for reload time.

Quote:
*EDIT* 1.5 lbs is freaky light for a longarm. Modern longarms are considered quite light and handy if they are around 5 lbs.
I wondered about that. I'm going to look up iron tubes and wooden stocks to check the mass.

I'll look into those other rifles you mentioned. Thanks.

EDIT: Found the Uberti 1873 Colt Buntline Special, .45 Colt, 18", with a listed shipping weight of 4.4 lbs compared to 2.3 lbs for the ordinary Colt Single Action Army it's based on. So that gives me a lower limit for the weight of my custom boomstick.

Last edited by TerryW; 03-06-2021 at 08:33 PM.
TerryW is offline   Reply With Quote
Old 03-06-2021, 09:08 PM   #5
DaosusLeghki
 
Join Date: Jul 2010
Default Re: Plausibility check for mixed TL3/4+2 firearm

Quote:
Originally Posted by TerryW View Post

EDIT: Found the Uberti 1873 Colt Buntline Special, .45 Colt, 18", with a listed shipping weight of 4.4 lbs compared to 2.3 lbs for the ordinary Colt Single Action Army it's based on. So that gives me a lower limit for the weight of my custom boomstick.
If it's for a 5 foot tall character, 3.5-4 lbs might be reasonable. The Colt revolver has a lot of metal that the much simpler one you are thinking about would not. Plus, you're using a 0.25 diameter projectile, which is quite tiny. Thus, it can have a fairly thin barrel.

But to be honest, I'm sort of nitpicking here. Your stats are realistic enough to be game-able.
DaosusLeghki is offline   Reply With Quote
Old 03-06-2021, 08:51 PM   #6
Polydamas
 
Join Date: Jan 2006
Location: Central Europe
Default Re: Plausibility check for mixed TL3/4+2 firearm

Manufacturing the weapon and manufacturing propellant are different engineering problems. Gunsmiths tended to have connections with other ironworkers and bronzefounders (especially locksmiths) while making black powder was connected with alchemy and medicine and sometimes dying or ceramics.

Quote:
Originally Posted by TerryW View Post
I have an idea for a mixed tech level firearm, as part of a time travel scenario. I know there are people on this board with much better knowledge of firearms than myself, so I thought I'd ask for a plausibility check.

The local TL is mixed 3/4. Basically a TL 3 nation (Early 14th Century Japan) next door to a more advanced neighbour. Japan doesn't train TL 4 craftspeople, but can buy their products or recruit craftspeople to work there. So I've tried to limit the technology, particularly the metallurgy, to materials available in late 13th Century East Asia. So no coiled steel springs for firing mechanisms. Instead the firearm uses a caplock mechanism powered by a small crossbow rather than a spring.
Powerful springs go way back, but fulminate of mercury for percussion caps was first perfected around 1814. They had automata in the Roman empire in the early middle ages, and European crossbows usually have little springs in the lock to reset the nut, so if you decide to go with percussion caps I suspect a spring is the more practical solution.
__________________
"It is easier to banish a habit of thought than a piece of knowledge." H. Beam Piper

This forum got less aggravating when I started using the ignore feature
Polydamas is offline   Reply With Quote
Old 03-06-2021, 08:52 PM   #7
Fred Brackin
 
Join Date: Aug 2007
Default Re: Plausibility check for mixed TL3/4+2 firearm

Quote:
Originally Posted by TerryW View Post
I h
The cartridge case is made of paper, the propellant is black powder, and I'm still trying to decide on the most likely primer.
If you're going to have someone invent percussion caps 500 years early it's going to be an alchemist screwing around with mercury. That doesn't narrow it down much as virtually all alchemists East and West screwed around with mercury but this would ahve to be someone who produced the useful explosive rather than only poisoning himself.

Mercuric fulminate was the original percussion primer anyway so it doesn't do anything exotic to stats.
__________________
Fred Brackin
Fred Brackin is offline   Reply With Quote
Old 03-06-2021, 09:18 PM   #8
TerryW
 
Join Date: Mar 2021
Default Re: Plausibility check for mixed TL3/4+2 firearm

Quote:
while making black powder was connected with alchemy and medicine and sometimes dying or ceramics.
I know you mean colouring with dyes but also yes alchemists spent a lot of time killing themselves.

Quote:
If you're going to have someone invent percussion caps 500 years early it's going to be an alchemist screwing around with mercury. That doesn't narrow it down much as virtually all alchemists East and West screwed around with mercury but this would ahve to be someone who produced the useful explosive rather than only poisoning himself.
It looks like the primer is impossible. I haven't been able to find any suitable explosive that could be manufactured with 14th Century methods without killing everyone involved. And probably their pets and neighbours too.

A flintlock will work just fine as a pleasant surprise for the other characters.
TerryW is offline   Reply With Quote
Old 03-06-2021, 09:55 PM   #9
Rupert
 
Rupert's Avatar
 
Join Date: Aug 2004
Location: Wellington, NZ
Default Re: Plausibility check for mixed TL3/4+2 firearm

Quote:
Originally Posted by TerryW View Post
It looks like the primer is impossible. I haven't been able to find any suitable explosive that could be manufactured with 14th Century methods without killing everyone involved. And probably their pets and neighbours too.

A flintlock will work just fine as a pleasant surprise for the other characters.
Mercury Fulminate could have been. Nitric Acid was possible at TL4, as was reasonably concentrated ethanol. Mercury has been known for a very long time. Managing to mix the stuff and collect the fulminate crystals without blowing oneself up would be difficult, but not impossible.
__________________
Rupert Boleyn

"A pessimist is an optimist with a sense of history."
Rupert is online now   Reply With Quote
Old 03-07-2021, 08:57 AM   #10
TerryW
 
Join Date: Mar 2021
Default Re: Plausibility check for mixed TL3/4+2 firearm

That might be more possible than I thought, then. We'll have to see what I can get away with in actual play.

Character creation session is coming up. 150 points, 10 points held back to reflect the steep learning curve we're going to face in the new era. We've been given the basic premise (Modern-era people transported back in time to early 14th Century Japan) so we won't waste points on things like Piloting or Computer Operations. The 10 CP will have to be spent on things we could plausibly pick up early on, like improved language skills or social connections.

Messaging the other players, so far it looks like we have:

> Three Japanese martial arts students, all from the same school. The GM gave them a basic school template, which includes a point each in Japanese history and dojo etiquette. We'll see if it occurs to any of them to improve those, but given that the players are all from a D&D background they probably won't.

> A professional cook from a rough streetwise background, who is also a hiking and outdoors type. Lots of potentially useful skills there.

> My character, the Canadian tourist. A fitness fanatic from a military family, with a masters in English Lit. Which lets the character have a range of skills and historical knowledge, but doesn't let me use my personal knowledge of the Northern and Southern Courts Period of Japanese history. It also means my character can't warn the other players not to show off their knowledge of japanese history, because she doesn't know that in that period fortune-telling and oracular rituals are monopolized by a government department.

Edit: Thanks, everyone, for your suggestions.

Last edited by TerryW; 03-07-2021 at 09:02 AM.
TerryW is offline   Reply With Quote
Reply

Tags
guns, tech level

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Fnords are Off
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 05:57 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.