[UT] Gun Generator v0.2

[Jinumon]

Greetings all,
You may remember me from this thread quite some time ago, in which I took my first crack at a system for building Ultratech firearms from the ground up. It has been a very long time since I first posted that, and I have continued to puzzle over this conundrum on and off since then. It has changed immensely in the time that has passed, mostly for the better. My ultimate goal is to get it to a Pyramid publishable state. As such, please feel free to play with the numbers, generate tons of guns, and give any suggests, critiques, or criticisms you think are warranted.

Before the meat of it, though, a few notes:
1) The mechanics only currently cover Conventional, rifled firearms. I intend on expanding it to include other projectile launchers and smoothbore, but I'm not there yet.
2) There are a number of anomalies that persist in the system as-is. I'm not sure if this is due to me missing variables, or because certain statistics were set arbitrarily, and thus have no definitive answer.
3) Certain formulas contradict intentionally with the source material. This is because, in some circumstances, I actually think my figures make more sense.

Special Thanks to David Pulver for his Eidetic Memory: Blaster and Laser Design article in Pyramid 3/37 and especially for his barrel length/bore size bit of wisdom. It has been an absolute Godsend.

Without further ado, here it is. Tell me what you think.

Jinumon

GURPS Gun Generator v0.2

The Variables:
When designing an Ultratech firearms, there are only five primary variables to be determined. From these five variables, all weapon statistics can be derived. They are as follows.

Configuration, the type of firearm (holdout, pistol, rifle, or cannon)
Simply select a configuration. Types are ordered from smallest (and lightest) to largest (and heaviest). The larger the configuration, the more accurate the firearm.

Bore Size, the diameter of the round, measured in millimeters
Select a round diameter. Larger rounds deal more damage, but will increase the size and weight of the weapon.

Relative Power, an abstract measure of the propellant/projectile ratio (low, medium, or high)
Select low, medium, or high. Most pistols have a low Relative Power, while most rifles have a medium Relative Power. High power is typically reserved for particularly high-velocity rounds, such as those fired from Anti-Material Rifles or rounds classified as “magnum” rounds.

Barrel Multiplier, the length of the barrel, measured in multiples of Bore Size
Select a barrel length (in millimeters) and divide it by Bore Size to find the Barrel Multiplier. A large Barrel Multiplier increases range, damage, and weight.

*A Note on Barrel Multiplier: Ultratech Weapons typically have shorter barrels than modern firearms. They range from 75mm (3 inches) in the Holdout Pistol, 7.5mmCLP to 800mm (32 inches) in the Payload Rifle, 25mmCL. Even the Anti-Material Rifle, 15mmCL only has a barrel length of 425mm (17 inches). Using modern weapons as inspiration may result in firearms heavier than expected. An alternative method is presented later.

Automation, the configuration of the firing mechanism (single-shot, semi-automatic, fully automatic, or rotary)
Select a level of Automation. Increasing Automation raises weight and rate of fire while reducing Legality Class. If you select “rotary” you must also select a number of barrels (typically 2 to 8).

Weapon Statistics:
Now that the variables have been selected, the individual statistics may be calculated

Damage (in dice) = Bore Size x Pd x cube root of (Barrel Multiplier) / 4
*Pd depends on Relative Power; 0.5 for low, 1 for medium, or 1.3 for high

Round partial dice as follows:
Damage Under 1d: 0.01 – 0.32 = 1d-5; 0.33 – 0.42 = 1d-4; 0.43 – 0.56 = 1d-3; 0.57 – 0.75 = 1d-2; 0.76 – 0.95 = 1d-1; 0.96 – 0.99 = 1d
Damage Over 1d: 0.01 – 0.14 = no modifier; 0.15 – 0.42 = +1; 0.43 – 0.64 = +2; 0.65 – 0.85 = +1d-1; 0.86 – 0.99 = round up to next full die

Damage Type is determined by Relative Power and Bore Size
Low Power is pi- for 7.99mm and smaller, pi for 8.00mm – 9.99mm, pi+ for 10mm – 14.99mm, or pi++ for 15mm and larger
High Power is pi- for 3.99mm and smaller, pi for 4.00mm – 9.99mm, pi+ for 10mm – 14.99mm, or pi++ for 15mm and larger

Accuracy is determined by Configuration
Acc is 1 for holdouts, 2 for pistols, 4 for rifles, and 6 for cannons

Range is determined by Bore Size, Relative Power, and Barrel Multiplier

1/2 Damage Range = Bore Size x Ph x 1.5 root of (Barrel Multiplier) x 8
*Ph depends on Relative Power; 0.35 for low, 1 for medium, and 1.9 for high

Max Range = 1/2 Damage Range x Pr
*Pr depends again on Relative Power; 12 for low, 6 for medium, and 4.5 for high

After calculating both 1/2 Damage and Maximum Ranges, round each number to 2 significant figures.

Rate of Fire is selected based on Automation.
1 for single-shot, 2 or 3 for semi-automatic, 4 to 15 for fully automatic, or up to 17 per barrel for rotary.

Shots
Simply select the number of shots in a standard magazine. Keep in mind that the more rounds in a magazine, the heavier the loaded weapon will be.

Weight = Empty Weight + (Weight Per Shot x Shots) + Magazine Weight

Empty Weight = Bore Size² x Barrel Multiplier x Pw x Aw / 375
*Pw depends on Relative Power; 0.5 for low, 1 for medium, and 1.5 for high
*Aw depends on Automation; 0.8 for single-shot, 1 for semi-automatic or fully automatic, or 1.2 (+0.5 per additional barrel for rotary)

Weight Per Shot = Bore Size³ x Pa / 25,000
*Pa is determined by Relative Power; 0.35 for low, 1 for medium, and 1.5 for high
Round to 2 significant figures.

Magazine Weight = Weight Per Shot x square root of (Shots)

An Alternate Method of Design
Because overall size and weight of a weapon is a major determining factor of whether or not someone will choose to use it, it may be advantageous to select the weight of the weapon ahead of time. To design a weapon this way, determine values for all of the five variables except Barrel Multiplier or Bore Size. With four of the five variables chosen, use the following formulas to find the last variable based on your selected Empty Weight.

Barrel Multiplier = Empty Weight x 375 / (Bore Size² x Pw x Aw)
or
Bore Size = square root of [Empty Weight x 375 / (Barrel Length x Pw x Aw)]

ST = square root of (Weight) x Cs
*Cs depends on Configuration; 3.2 for rifles, 3.5 for cannons, and 4.8 for pistols and holdouts

Round to the nearest whole number. Listed values are one-handed for holdouts and pistols, two-handed for rifles and cannons.

Bulk = square root of (Weight) x Cb
*Cb depends on Configuration; 1 for holdouts, 1.25 for pistols, or 1.5 for rifles and cannons

Minimum Bulk is 0 for holdouts, -1 for pistols, -3 for rifles, or -6 for cannons. Maximum Bulk is -10

Recoil
Rcl is dependent upon Bore Size; 2 for 7.99mm and smaller, 3 for 8.00mm – 11.99mm, or 4 for 12mm and larger

Cost = Empty Weight x $300
Round to 2 significant figures.

*A Note on Firearm Cost:
Contrary to popular belief, the Automation or, more specifically, the Rate of Fire, does not affect the cost of a firearm. In fact, the difference between a semi-automatic and fully automatic weapon is rarely more than an extra step in the factory and a few dollars in parts. Any increase in cost due to Automation is instead due to either rarity or government restriction of automatic weapons. The Cost given for weapons is effectively wholesale. Should players wish to acquire automatic weapons in play, they will likely have to skirt the law to acquire them, or pay substantial premiums on the black market.

Cost Per Shot = Weight Per Shot x $20

LC
Base LC for Conventional Firearms is 3. Reduce the LC by 1 if the weapon is fully automatic, or by 2 if the weapon is rotary. Reduce LC by an additional 1 (minimum 1) if Bore Size is 20mm or greater.

[Dwarf99]

I remember your old system. I was inspired to create a separate system where everything was based on the bullet instead.

1/2d ranges scale with the standard caliber and Max ranges are on par with that. It would not be outrageous to assign 1/2d ranges of Caliber(in mm)x(20 yards) and Max Ranges of (Case Length)x(100 Yards)

I used Case Lengths of Caliberx2 for pistol rounds and Caliburx5 for rifle rounds. I wrote a big table for damage by caliber that was about 15% off (10mm was 2d for a pistol and 5d for a rifle, for example).

Damage was based on reducing Spaceships numbers by using their dDamage as iDamage and converting cm to mm. There were some numbers tweaks as well, because I wanted to consolidate 20mm firearms with 2cm cannons.

I like your system better where you have a more abstract Relative Power. I like that you have math that's easier than ballistics calculus, but not more or less grabbed from a table and tweaked to taste.

[Jinumon]

Originally Posted by Dwarf99

I like that you have math that's easier than ballistics calculus, but not more or less grabbed from a table and tweaked to taste.

Thanks. Essentially everything is reverse-engineered from Ultratech and Pyramid 3/37: Tech and Toys II. If you don't have the issue, I'd suggest picking it up, even if it's solely for David Pulver's Blaster and Laser Design. Douglas Cole's Interior and Terminal Ballistics also helped me get a better understanding of ballistics in general too. I can't speak for the scientific accuracy of my system, but it does seem to produce results very close to the source material in most cases.

Jinumon

[LemmingLord]

I am saddened. I misread the thread title and has been looking forwad to easily generating some nun characters.

[Dwarf99]

Originally Posted by Jinumon

Thanks. Essentially everything is reverse-engineered from Ultratech and Pyramid 3/37: Tech and Toys II. <snip>Blaster and Laser Design.

I'm familiar with that.

Douglas Cole's Interior and Terminal Ballistics also helped me get a better understanding of ballistics in general too.

I was talking about that but I couldn't remember what it was called.

I can't speak for the scientific accuracy of my system, but it does seem to produce results very close to the source material in most cases.

That's ok. To me it's simple and that's what matters. Case in point: I wrote a d20 system mod whereby I took all the cartridge diameters and case lengths I could find. Damage for rounds that weren't necked down was 1/2 Diameter dice, and full diameter for those that were. Number of dice was the ratio of Length/Diameter. For odd results like 8d3, invert the numbers. Problem solved, and it was less arbitrary than the d20 Weapons Locker. Somewhere between scientifically accurate and arbitrary, where the balancing factor was simplicity.

[Jinumon]

I'm hoping to eventually get it to a point where guns can be procedurally generated, a la Borderlands. Being able to create guns on the fly for enemies or for looting purposes has always sounded like an awesome addition to a gritty Space-Western.

Jinumon

[Dwarf99]

So out of curiosity (I know it's not a UT weapon, sorry) I tried to apply all this math to a revolver I like to put in my Fantasy games. I call it the Gnomish Hand Cannon. It's .50 cal pistol, Low Powered, with an 8 inch barrel

Damage: 12.7x.5x2.5/4=4d pi++
Acc: 2
1/2d: I don't know what the 1.5 root of 16 is If it's 6, the 1/2d is 12.7x.35x??x8=~215 yards.
Max: If the 1/2d is correct, Max is 2,580.
RoF: 3
Ewt: 161.29x16x.5x1/375=3.44 lbs
WPS: 2048x.35/25,000=.02
Blk: 1.8x1.25=2.3 but Maximum is 1.
ST: 9
Rcl: 4
Cost: $3,100

In comparison to my old stats, the damage and range are pretty close. the Ewt and ST are a bit lower than expected. That might be solveable saying that a "Magnum" pistol round is medium power (if I'm any guess, they'll be about 7 lbs and 12 ST maybe which are actually slightly preferrable to my original values.)

[Jinumon]

Originally Posted by Dwarf99

1/2d: I don't know what the 1.5 root of 16 is If it's 6, the 1/2d is 12.7x.35x??x8=~215 yards.

Calculating 1.5 root requires some button wizardry on an advanced calculator. A simpler way to calculate it is 16^(2/3) (to the power of the reciprocal of 1.5), or 6.35.

Originally Posted by Dwarf99

Blk: 1.8x1.25=2.3 but Maximum is 1.

Minimum Bulk is -1, as in it cannot go lower that 1. Bulk is -2, rounded from 2.3.

Jinumon

[Langy]

Originally Posted by Jinumon

Minimum Bulk is -1, as in it cannot go lower that 1. Bulk is -2, rounded from 2.3.

Jinumon

No, you got that wrong. Maximum bulk is -1; minimum absolute value of Bulk is 1.

Remember that Bulk is calculated as a negative number.

[Jinumon]

Originally Posted by Langy

No, you got that wrong. Maximum bulk is -1; minimum absolute value of Bulk is 1.

Remember that Bulk is calculated as a negative number.

I know, technically. But, to be fair, one could say the minimum penalty is 1. Additionally, it's a minimum size for the weapon.

Anyway, semantics. I think people understand what I mean.

Jinumon