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Old 03-07-2021, 09:38 AM   #11
whswhs
 
Join Date: Jun 2005
Location: Lawrence, KS
Default Re: Plausibility check for mixed TL3/4+2 firearm

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Originally Posted by TerryW View Post
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.
I addressed this somewhat differently in GURPS Fantasy: Portal Realms. A quick sketch is that characters could buy anything they liked in the modern setting, but if it didn't apply in the portal realm its cost was 0 points. In particular, they could take any Wealth they liked, but they would be limited to what they were able to take with them, and that would be used to determine a new Wealth level (treating them as nomadic characters all of whose wealth was on their persons). That allowed characters to have more detailed backgrounds without having to pay points for things that are, as you say, a waste.
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Old 03-07-2021, 11:42 AM   #12
TerryW
 
Join Date: Mar 2021
Default Re: Plausibility check for mixed TL3/4+2 firearm

We've been told to keep our investment in social advantages (Wealth, status, etc) low, but we'll be allowed to reassign those points as the game progresses. So I could "bank" up to 20 CP in reputation and status, to be reassigned over the course of a few game sessions. The example the GM gave us: if someone started as a cop with a good reputation and a contact, they could quickly impress the locals with their demeanor and "obvious sound moral character" and justify spending those points on earning a new rank and position.

But of course those banked points will be useless in the first session, and will remain useless until campaign events justify reassigning them. It doesn't look like any of us took the trade-off of starting off weak but rising through the ranks quickly.
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Old 03-07-2021, 12:18 PM   #13
Varyon
 
Join Date: Jun 2013
Default Re: Plausibility check for mixed TL3/4+2 firearm

I'm not familiar with Luke's firearm design system, but in GURPS Classic: Vehicles (from 3e), breechloaders are 50% heavier than muzzleloaders, so your weapon should probably be around 2.25 lb.

Your loading mechanism is... interesting. It sounds like, rather than using the paper cartridges normally (where you break it open, pour in the powder, and use the paper for wadding), you want to have the paper cartridge take the place of a metal cartridge, with the whole thing loaded in. Given you're going to be using a flintlock mechanism, I think a variant of an idea I had in the past might work for you. You basically add a small hole where the cartridge is when loaded (which I think you need anyway for a flintlock) and add a very small pin to the rifle (attached by a short lanyard, or otherwise movable; note you want a similar method for the plug). Load the paper cartridge from the rear (sorta like a break-open rifle, or a zip-gun), seal it in, poke the pin into the hole, and create a powder trail into the flash pan - this primes the pan and creates a path to the loaded powder, allowing you to use the flintlock normally.

As for pi-0.5, that's what GURPS calls Pi- (Luke uses a houserule that expands the piercing classes, so it uses different abbreviations), as in it has a Wounding Multiplier of x0.5. For reload time, breechloading rifles canonically have a 10 second reload time, which is cut in half (to 5 seconds) by using a paper cartridge. However, that's using a paper cartridge normally. With a metallic cartridge, you'd also be looking at 5 seconds - one to open the breech, one to eject the spent cartridge, one to draw the ammo, one to insert it, and one to close the breech. Your mechanism sounds like it should take longer to open and close the breech, although I don't think it would take a full extra second for each. I'd say 1.5 seconds to open, 1 to draw your ammo, 1 to insert it, 1.5 to close the breech, 1 to use the needle to puncture the cartridge (priming the flash pan), and 1 to cock the lever, readying the weapon to fire. That's 7 seconds to reload - note there's no time needed to remove the cartridge (as it's been burned up).
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Old 03-07-2021, 01:27 PM   #14
johndallman
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Default Re: Plausibility check for mixed TL3/4+2 firearm

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Originally Posted by Varyon View Post
. . .I think a variant of an idea I had in the past might work for you. You basically add a small hole where the cartridge is when loaded (which I think you need anyway for a flintlock) and add a very small pin to the rifle (attached by a short lanyard, or otherwise movable; note you want a similar method for the plug). Load the paper cartridge from the rear (sorta like a break-open rifle, or a zip-gun), seal it in, poke the pin into the hole, and create a powder trail into the flash pan - this primes the pan and creates a path to the loaded powder, allowing you to use the flintlock normally.
This sounds simpler than trying to create percussion caps with marginal technology. Two things that could improve the process:
  • Soak the paper in a potassium nitrate (saltpetre) solution and let it dry before making up the cartridges. This ensures the paper burns up fully, so that you don't have embers in the barrel, hiding under fouling, waiting to ignite the next cartridge when you load it.
  • Coat the finished cartridges in "waterglass," if you can get it. This makes them more robust, and can be used as a glue to hold the paper wrapping together.
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Old 03-07-2021, 03:48 PM   #15
TerryW
 
Join Date: Mar 2021
Default Re: Plausibility check for mixed TL3/4+2 firearm

Thanks again. Character creation and first session is tonight. I'm going to send my notes to the GM and bookmark this thread for him, for future reference.

Getting to the point where my PC can start hiring craftpeople to make all this will involve a lot of work. And all of this assumes that the characters survive long enough to get started on it.
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Old 03-07-2021, 04:37 PM   #16
Willy
 
Join Date: Dec 2020
Default Re: Plausibility check for mixed TL3/4+2 firearm

As far as I cremember therer was a gun like this in history, it added to all this a half screw at the end of the barrel, so with one 90 degree turn you can pull it out, half of the thread is filed down to make this possible. This speeded up the reloading time a bit, and was gas tight enough not to endanger the shooter.

Sorry for bad english I don´t know the technical term for this exactly
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Old 03-08-2021, 04:41 AM   #17
dcarson
 
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Default Re: Plausibility check for mixed TL3/4+2 firearm

S. M. Stirling in his Island in the Sea of Time had them use paper cartridges with a felt disk as the base. Helped seal the breech and when you pushed the next cartridge in the felt was fired on the tip of the bullet to sweep the barrel lower how fast the black powder fouled the barrel it
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Old 03-08-2021, 05:32 AM   #18
DanHoward
 
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Default Re: Plausibility check for mixed TL3/4+2 firearm

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Originally Posted by Rupert View Post
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.
I'm pretty sure you need fuming nitric acid to make mercury fulminate. Regular nitric acid might be possible at TL4 but not fuming nitric acid.
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Old 03-08-2021, 05:50 AM   #19
Anders
 
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Default Re: Plausibility check for mixed TL3/4+2 firearm

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Originally Posted by Rupert View Post
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.
I'll ask around at a chemistry Discord I'm on.

Edit: Fuming nitric acid is not necessary.
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Last edited by Anders; 03-08-2021 at 05:55 AM.
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Old 03-08-2021, 06:17 AM   #20
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Default Re: Plausibility check for mixed TL3/4+2 firearm

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Originally Posted by dcarson View Post
S. M. Stirling in his Island in the Sea of Time had them use paper cartridges with a felt disk as the base. Helped seal the breech and when you pushed the next cartridge in the felt was fired on the tip of the bullet to sweep the barrel lower how fast the black powder fouled the barrel it
Of course, probably the most famous alternate-technology note from divergent history is from Eric Flint's 1632 series and concerns the method of manufacturing percussion primers with lower-tech chemistry that a reader came up with and demonstrated, changing the whole storyline of forthcoming books, as Flint realized that while his modern characters used the methods known from textbooks, natives of the 17th century could have independently developed the other method, as the reader does, when they heard about the possibility of the technology.
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