GURPS Demolitions: Custom Shrapnel

 GURPS Demolitions: Custom Shrapnel

Explosives are fun. Adventurers are always able to find things to blow up, such as Cthulhu spawn or a werewolf or a nazi tank. Except, in GURPS, the concussive force of the explosion runs out of steam very quickly. Man-portable charges are rarely lethal at 5 yards, let alone 10, so a person may feel discouraged when a big boom doesn't really kill anyone.

How is the issue resolved IRL? Well, one solid way to increase your explosive's lethality is to encase it into shrapnel-creating object. That's how a hand grenade is made - fragmenting shell and an explosive charge.

GURPS does not readily have rules for custom shrapnel explosives, but with the help of Kromm's post and Kalos's math affinity, there is now a way to create custom shrapnel for your satchel charge.

1) Take your explosives and figure out it's damage using rules on B414.

2) Gather shrapneling material.

3) Roll Explosives (Demolitions) to assemble the device. Success by 0 yields a device with up to 1:1 ratio of shrapnel and explosives. For example, 1 lb of C4 can have up to 1 lb of shrapnel, for total of 2 lb. This is equivalent to a pipe bomb in box on TS67.

For every success after 0th, you can decrease the amount of explosive needed by 5%, or increase amount of shrapnel by 5%. Maximum ratio is 19:1, with only 5% of the device being explosives. This is equivalent to factory made aircraft bombs!

4) Calculate shrapnel damage using this formula: 

x^1/3*2.35, result in dice

x=shrapnel material weight in lbs

5) Record the device's statblock: It's explosive damage, it's shrapnel damage and weight of the device.

Example:

A Werewolf Hunter wants a handmade explosive that launches silver shrapnel but doesn't explode too hard.

He takes 1 lbs of Liquid Explosive Foam (REF 1.1) and prepares a smithy to forge silver casing.

He rolls Demoliton (Explosives) and succeeds by 9, creating a very-well designed device with explosive content of only 5%.

If he wants to, he can create a 2 lbs portable satchel, with 0.1 explosive and 1.9 shrapnel material.

1.9^1/3*2=2.47 or 2d+2, see box on HT166

End result: Dmg 4d [2d+2] cr ex, Wt. 2 lbs

If he wants to, he can encase 1 lbs of explosives in 19 lbs of shrapnel, retaining the 19:1 ratio.

19^1/3*2=5.33 or 5d+1

End result: 26d+1 [5d+1] cr ex, or 6dx4+8 [5d+1] cr ex, Wt. 20 lbs.

Optional rule: Involving explosive's REF

If you have noticed, shrapnel damage has no relation to how much damage the explosive outputs, or it's REF. Folks in the thread that the Krommpost is from insist that it is realistic.

If you believe otherwise, feel free to divide the final weight of explosive filler by it's REF. Assume everything above was said about REF 1 explosive.

For example, you assemble a device that is 1 lb shrapnel and 1 lb REF 1 explosives for a total of 2 lb. If you use REF 1.4 plastic explosive instead, you only need 0.7 lbs of it to achieve the same result as 1 lb REF 1 charge. The device's final weight is 1.7 lbs when using plastique. One must be careful with this optional rule, as it allows miniscule amounts of explosive (like REF 5 Fuel-Air mixture) propel teeth-shattering amount of shrapnel. Alternatively, an unskilled person can make more effective bombs if they just use a higher REF explosive.

Notice, the damage from the explosion is STILL related to the weight of explosive. Using less explosives means the explosive damage is reduced as well. This only allows you to further reduce explosive to shrapnel ratio.

GURPS Firearm: ALFA .357 Magnum, UK-Legal Muzzleloading Caplock Revolver

 GURPS Firearm: ALFA .357 Muzzleloading Caplock Revolver

Ah, United Kingdom. Homeland of tea parties, colonialism and quirky weirdos who save the world from weekly calamities (that mostly happen in London). They also have great gun laws that allow one to own such beautiful handguns like these:

Just kidding about the last one. But yeah, handgun ownership in UK is not the same as it was at the start of 20th century. Doctor Watson had to turn his Webley in, and his modern counterpart from Sherlock is straight up breaking the law as he runs around modern-day London shooting an illegal, smuggled in SIG P226. None the less, inventive people exist, and they readily find loopholes in the law to permit their fellow countrymen to enjoy handgun shooting like proper gentlemen.

Meet ALFA Series .357 Muzzleloading Revolver

ALFA .357 begins it's life as bona-fide cased cartridge .357 Magnum revolver, built in a Czech factory. It's relatively unknown, and is built for civilian market. The magic happens when it's almost complete. A number of ALFA .357s are sent on to a small, grassroots manufacturer in UK without a cylinder - technically not a firearm since it cannot chamber or shoot anything. The manufacturer, Westlake Engineering, assembles their own cylinder, but not a typical one. This cylinder operates on a caplock design, like early TL5 revolvers of the Wild West, requiring all the proper stuff of filling the slots with powder, pressing a bullet in, sealing it with a cap, etc, the difference being - it uses smokeless powder and modern .357 projectiles. This is an ingenious design, as UK gun laws do not regulate the length of muzzleloading firearms, allowing to dispose of weird shoulder things and to have any conceivable barrel lengths.

This weapon is LC3 in UK, being legally a muzzleloader, only requiring a basic firearms permit to own. The weapon has to be registered, alongside any spare cylinders, and the license usually holds up to 5 items, allowing for 1 Revolver and 4 spare cylinders. Spare cylinders are costly, usually no less than $250, Wt 0.3, but the weapon itself comes with two - one in gun, one spare.

Performance-wise, recommended loadings output behavior on par with .38 Spc. While the revolver itself is able to sustain .357 loads, the cylinder is less reliable - if using .357 Magnum loadings, Malf 16. Available projectiles are Solid and Hollow-Base Wadcutter (Treat as Solid and Hollow Point, respectively). WPS and CPS remain the same as with cased cartridges, use either .38 Spc or .357 Magnum values depending on load.

Weapon comes in 4 barrel lengths:

6" - In table

4" - 2d pi, bulk -2,  Wt 2.1/0.3

3" - 2d-1 pi, bulk -1, Wt 1.9/0.3

2" - 2d-1 pi, bulk -1, Wt 1.8/0.3

Magnum loadings:

6" - In table

4" - 3d-1 pi

3" - 2d+2 pi, rcl 5, ST 11

2" - 2d+2 pi, rcl 5, ST 11

Reloading is the same as for all cap&ball revolvers, (10i). Speedloaders are impossible. On the bright side, the cylinder is not held in place, so it can be swapped out rather quickly. Shooter can pre-load all of his cylinders at home and simply swap them out as the firefight goes.

1: Swing the cylinder out
2: Remove the cylinder and discard it. Keeping it is an extra Ready maneuver.
3: Draw a spare cylinder

4: Insert the cylinder onto it's base

5: Swing the revolver closed

In short, it's a solid piece for a civilian UK gun owner, something to defend yourself from a robbery, or while investigating a murder mystery. The weapon can come with a mount for sights and other improvements for sporting use, making fine (accurate) variants available. Do note that UK frowns upon any self-defense, armed or not, so consult your GM regarding all this, and don't use my advice on the matter IRL.

.gcs file (4.2)

Credits to Kalos for helping me figure out the damages and range of this thing.

GURPS Homebrew: Binary Trigger Pack

 

GURPS Homebrew: Binary Trigger Pack Gunsmithing Option

We all watched the movies or played the games where a brave commando fires his gun full auto, destroying his enemies in droves as an inspirational battle track plays in the background. That's how many people got into guns as a hobby, even. Similar to how many car enthusiasts started enjoying cars after seeing an F1 grand prix.

And while car owners can still head over to the racing track with their street cars and break a few limits while drifting a few corners, civilian gun owners are forbidden by law to own a weapon capable of automatic fire, sans some exceptions. And so, weapon engineers set out to find a loophole in the law and assemble a legal device that would give a civilian firearm a semblence of automatic fire. 

And the loophole was, your firearm must fire only once per trigger pull. But trigger release is not mentioned.

Binary Trigger Pack (TL8)

$400, neg, LC3

This device replaces standard safe-semi trigger and fire control group with safe-semi-binary. While the weapon functions as normal in safe-semi modes, the new binary mode functions unlike any other firearm. In binary mode, when you pull the trigger, a bullet is fired. Then, when you release the trigger, another bullet is fired. Effectively, a weapon fires twice per trigger pull! Treat it as 2-round Limited Burst (HT83). Due to the system's unique behavior, those unfamiliar with a firearm that has it suffer an extra -2 familiarity penalty (-4 total) to Guns skill. The second shot's discharge can be canceled by moving safety selector to semi or safe while the trigger is held down (Ready maneuver or free with Lightning Fingers).

These devices only work with semiautomatic weapons, and each one is designed for specific system (AR15, Glock, H&K G3 etc), but designs are available for virtually all popular semi-automatic firearms, including rifles, pistol caliber carbines (civilian SMGs), semiautomatic shotguns and pistols as well. Installation is treated as Adding Accessories (TS68) and is a Complicated process. The weapon's ROF changes to 6 and it operates as if it has 2-shot Limited Burst (HT83).

This design originates in the USA and in majority of states it is an LC3 device, although some states have moved to independently ban it, making a firearm with binary trigger an LC2 weapon. Outside of the US, such designs are rare and most jurisdictions do not include the same loophole as US gun laws, making the item itself LC2. Despite that, due to design's novelty, one can still try to import and install it, since laws seldom have provisions to forbid it. A good lawyer is recommended still.

In situations where law is of no concern, such device could be part of a unique weapon, or used by folks who need firepower, but are unable to acquire actual automatics. It is also much safer to install on a firearm than trying to convert it to full-auto via homemade measures, and limited RoF ensures the gun doesn't beat itself to death.