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 04-03-2017, 09:43 AM   #31
hal
 
Join Date: Aug 2004
Location: Buffalo, New York
Default Re: GURPS ULTRATECH ballistics?

This isn't a dig against your work Hans. The formula I used pretty much maches the samples from GURPS ADVENTURE GUNS, which seemed pretty convincing the formula works. Were I to compare old GURPS stats against the new, I'd expect there would be those that didn't match as the formulas seem to be different.

So - the reversed formula gets the job done for black powder weapons, but not for the H&K G11. I did allow for the possibiliy that it might be off and you'd be aware of why. You've just confirmed it now. ;)

The fine tuning aspect, implies things to me that either more goes into the damage formula than Doug's Formula provides, or that David's Formula isn't exact enough that it requires Tweaking. Since the formula isn't readily a available, all we can do is compare results between the one formula's results against the published material and try to figure out why.

I doubt that every gun that ever existed will be statted out by SJGames. If some wants to stat out a gun for their campaign using real world stats - this would be one way to go about it. Doug's formula combined with published data on ammunition stats, gives a baseline only. When the published material specifies a given mass for the bullet, what gun was used to fire that bullet? What was the barrel length? What other factors can come into play? But, until the design formulas for guns are published akin to what was in GURPS VEHICLES, we can only speculate
hal is offline   Reply With Quote
Old 04-05-2017, 12:07 PM   #32
shadowclad
 
Join Date: May 2012
Default Re: GURPS ULTRATECH ballistics?

Quote:
Originally Posted by HANS View Post
Bear in mind that Doug's unofficial formula is reverse-engineered and does diverge in certain assumptions from the one developed by David Pulver (math) and me (fine-tuning and reality checking against hundreds of data points) ages ago, I think in 2002 or 2003 or so. This was used for the weapon stats in all recent High-Tech books. I find it difficult to see how you can see a discrepancy when you're not using the official formula. Yeah, I know, the formula itself is unpublished, but the results aren't. They are in all my books, which are internally consistant.
Hey, Hans,

I hope this isn't rude or in violation of the forum rules, but since you were a credited playtester on Ultra-Tech 4e, can I ask you about the firearms stats, either in the thread or privately? I swear I will not ask you about the unpublished formula. :)
shadowclad is offline   Reply With Quote
Old 04-09-2017, 10:01 PM   #33
Milano
 
Join Date: Apr 2017
Default Re: GURPS ULTRATECH ballistics?

Years ago I made a spreadsheet to do the weapons for Twilight 2000. Being a sadist I went ahead and started doing the recipes for the other rpgs that I enjoy, and am still working on it as you can see.

I only recently bought GURPS 4e and am not very comfortable with the rules yet. However, I thought that this excel file may be of some value to any designs that you all may want.

The program is to realistically use Ballistic Coefficients, Sectional Density, and Cartridge data to portray small arms that are currently in existence. TL5-9 (I think. See above.) I reload ALOT. I shoot competitively ALOT. I do not use Excel a lot so please excuse some errors.

The realism parts are on tabs called Ballistics Table and Ammunition Table.
From the real external ballistics look at columns D-N and U - AA on the Ballistics Table tab. These are not guesses or gamey. These are formulas that I got out of Brian Lytz's book about ballistics (I think).

The Ammunition Tab has 210 different Cartridges that are typically used in hand held small arms. (The RT-20 and it's 20mm cannon rounds are debateable but you get the point... 210.) Like I say I reload for many different calibers and I have access to a whole bunch of information. The Cartridge in colums M, N, and O are real. Just because the 45-100 Sharps was also known as the 45 2 6/10" I did not assume. I looked it up from Mike Venturinos book, Shooting Buffalo Rifles of the Old West.

On the same tab is the table A:3 to H: 248 these are the individual bullets that are used for the cartridges. These are all real bullets by manufactures (Barnes, Sierra, etc) or taken from verified sources for military bullets (for example the M903 50 BMG SLAP round). Take note that for example there are 12 different weight 0.224 bullets for 22-250s, 220 Swift, 5.56x45, etc. In column F are the Ballistic Coefficients. They are the G1 BCs, the G7 work well for BTHP bullets but not so well for all others LRNFP, JHC, etc. The G1s are my allowance for consistency. Note that I did have to make some wild and educated guesses. These BCs are color coded so that IF someone figures out the BC of the Chienese DAP92 5.8x21 pistol round they can correct my guess. Column G is the calculated Section Density. Column H has notes on basic velocity and published penetration data for comparison.

The tab Weapon Data is where you input you firearm and cartridge data. Column B is to be filled in with the weapon data. Barrel length, sight radius, ROF, etc. Note on Rate of Fire, there are two ROF inputs one is to be used for burst weapons like MP5a2. They fire in both a burst, 2 or 3, and Full Cyclic. You will have to adjust the burst ROF to get the desired out comes. For example in TW2000 I divide the Real ROF by about 120. This is a half second burst for Assault rifles and by 100 for MGs. The rationale being that MGs are usually fired for another round or two longer than a center mass point target like from an M4. This can be changed on tab Twilight 2000 J:2-J:9. Cells B:8-B:11 are tabs. Select what is best representative of the weapon you are statting out. ie Assault Rifle, Sub Gun, Standard, Bullpup, etc.

D:1-E:7 is the cartridge data. Most of it is selectable tabs. DO NOT write in D:9-E:14, all this data is collected as you fill out the green boxes above. Note that in D:16 are usually notes on real life published data for velocity, penetration, etc. For example the M193 5.56x45 round has variable velocities of 975-990 m/s. Because of many variables I would take an educated guess or use data you find. My specific HBAR sends them at about 3225 f/s. Note that cells E:5-F:6 there is a handy conversion. Type in 3225 in cell E:6 and whaalah in cell F:5 is the m/s conversion of 982.98 m/s.

Cells A:24-J:27 are some common diagnostic formulas for bullet impacts at ranges of 5, 100, 300, 600, and 900 meters. Note: I started this again for Twilight 2000 using Fire Fusion and Steel. Their fakeary formula is in A:31. OGW= Optimum game weight, I used large animal formula.

Finally the Weapon tab is where all the data is collated and put into more readable form. Thus far is the data for TW2000 and Phoenix Command.

I wish I have had the time to offer a finished product, but I don't. With 2 kids 2 full time jobs and a working wife it's not looking good before 5e is released. So, I offer it as it is. Hopefully after reading this thread about 1,122 times I have a handle on what formulas I have and need to start statting GURPS small arms.

What I would ask are a few things:
Please let me know of any mistakes in the tables. I have not finished what I wanted yet. (Take note of Weapon L:12, I need to fix this. This is the range that a supersonic bullet breaks the sound barrier and becomes way less stable and accurate.)
Also as people comeup with formulas for ST, Range, etc please update this tread maybe? It would be nice to have a consensus of formulas in one place. Or did I completely miss it?
Any help to where formulas can be found would be GREATLY appreciated and it would help me to add GURPS to this one and re post it.
Any questions, please ask me. I would like to be more thorough but.. I am "wordy" as it is. I would like to have the community use every tool at their disposal, well. So ask me, please.
Also no money can be made by using this spreadsheet by anyone. I offer it as is and trust that it is for personal use. I also accept no liability. If you're going over there and use this as your DOPE well... for my conscience please don't. I can help you with that and not by using this spreadsheet.



https://www.dropbox.com/sh/70hj7hoe2...CCv7S0vxa?dl=0
Milano is offline   Reply With Quote
Old 04-09-2017, 10:04 PM   #34
Milano
 
Join Date: Apr 2017
Default Re: GURPS ULTRATECH ballistics?

Randomly I REALLY want to finish TW2013. If anyone plays or has any insight to those formulas I would Adore you for it. Many of the weapons seem to be 2+2=4 except this rifle, that pistol and well as all Carbines...
Milano is offline   Reply With Quote
Old 04-10-2017, 01:12 AM   #35
hal
 
Join Date: Aug 2004
Location: Buffalo, New York
Default Re: GURPS ULTRATECH ballistics?

Hello Milano,
Welcome to both GURPS, and the GURPS FORUMS. Thank you for your post and your offer. I've sent you a private email on this topic for reasons regarding the offer of your excel spreadsheet and my offer to help you to "tidy it up".

Protecting Cells in Excel is rather easy if you know how, and a "I didn't know it could do that" if you don't know how. :) We're all neophytes with software packages until we read a book on how to work with it, or have someone show us how. For the longest time, VBA (Visual Basic for Applications) was a mystery to me, until one day at work, I found that my knowledge of VB.NET was a good stand-in default skill for VBA. I consider VBA to be VB.NET's less intelligent or less capable cousin as it were. An application I wrote at a bank to process some information would take nearly 20 minutes to work its way though, whereas a complied VB.NET application would only take about a minute or two to process the same data. Go figure eh? ;)

In any event, let me know if I can help or not via the private email...

Hal
hal is offline   Reply With Quote
Old 04-10-2017, 11:20 AM   #36
Milano
 
Join Date: Apr 2017
Default Re: GURPS ULTRATECH ballistics?

I emailed you.... I think. ;)

It occurred to me last night that I've never used drop box before and if anyone is nervous about using it and has another avenue to get you the file let me know, I am all ears.
Milano is offline   Reply With Quote
Old 09-21-2017, 02:48 PM   #37
hal
 
Join Date: Aug 2004
Location: Buffalo, New York
Default Re: GURPS ULTRATECH ballistics?

Quote:
Originally Posted by Fred Brackin View Post
Ammo weights might be the most hashed up numbers in UT. I doubt you can do anything sensible with them.
Hi Fred - at the risk of engaging in thread necromancy here, I took a fresh look at the data, trying to find ways to maybe use HIGH TECH guns repurposed to a TL 9 standard instead of TL 8 standard.

One thing you stated above just got confirmed.

Looking at the real world data on the Rifle round for the G11 4.73x33mm round, the weight of the bullet is 3.1 grams (49 grains) and the weight of the round is 12.05 grams (186 grains). That produced a round velocity of 3051 feet per second or 930 meters per second.

So, I did a look up on how many grains to the pound as well as how many grams per grain.

There being 7000 grains to the pound, we can switch between real world measures of bullets and rounds when talking about ULTRATECH rounds as given in the 4e version of Ultratech. Thought you and others might find it interesting...

Multiply the WPS on page 139 by 7000, and that gives you the number of grains per round in weight. For reference, the G11 round was 186 grains, or would weigh roughly .027 lbs per round. High Tech says .011 lbs per round, so there is something of a discrepancy there. Could be simply difference references (I used THE GREENHILL MILITARY SMALL ARMS DATA BOOK by Ian V. Hogg in this instance, published 1999).

Using the formulas outlined above...
Code:
		WPS	Grains
7.5mm		0.006	42			
10mm		0.014	98			
15mm		0.06	420			
						
5.7mm		0.013	91
7mm		0.027	189
10mm		0.04	280
10mmCLR		0.06	420
15mm		0.2	1400
If roughly 25 to 26% of the round weight is the bullet weight (just an assumption based on the 1:2.89 ratio for the G11 round) then we can arrive at some values based on the numbers given in ULTRATECH.
hal is offline   Reply With Quote
Old 09-25-2017, 04:26 PM   #38
hal
 
Join Date: Aug 2004
Location: Buffalo, New York
Default Re: GURPS ULTRATECH ballistics?

Question for you gents out there...

What is the difference between Average damage 9 points, where the dice rolled is 2d6+2 and 3d6-1

If the average roll for 1d6 is 3.5, then 3d6-1 is actually average damage 10.5-1 or 9.5

Is that the difference between weapons rated at 2d6+2 and 3d6-1?

For example, when I plug in the velocity in feet per second, diameter, and bullet weight for a 10mm automatic pistol round, I get 2d+2, whereas in GURPS HIGH TECH, the damage for he Glock 20 (using the 10mm Automatic) is listed at 3d-1

Just curious...
hal is offline   Reply With Quote
Old 09-25-2017, 04:38 PM   #39
sir_pudding
Wielder of Smart Pants
 
sir_pudding's Avatar
 
Join Date: Aug 2004
Location: Ventura CA
Default Re: GURPS ULTRATECH ballistics?

GURPS generally favors increasing central tendency in firearm damage values up to six or seven dice.
sir_pudding is offline   Reply With Quote
Old 09-25-2017, 04:56 PM   #40
hal
 
Join Date: Aug 2004
Location: Buffalo, New York
Default Re: GURPS ULTRATECH ballistics?

Quote:
Originally Posted by sir_pudding View Post
GURPS generally favors increasing central tendency in firearm damage values up to six or seven dice.
I can go with that. Problem is...

When some gun damage stats are listed as being 3d6-1 and I get a calculated stat of 2d6+2 (both are average damage of about 9) then I have to try and figure out why it might be 3d6-1 instead of 2d6+2

I'm guessing that it all depends on whether average damage is 9.5 or if the average damage is 9.0.

In game play, using say, 3d6-2 for weapon damage is about 8.5 average. Minimum damage is 1, maximum damage is 16, but average works out to 8.5 On the flip side, using 2d6+1 averages to 8.0 with a minimum damage of 3, and a maximum damage of 13.

Which would most gamers look at saying "I would prefer this over that"?
hal is offline   Reply With Quote
Reply

Tags
high-tech, ultra-tech

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 05:35 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2018, vBulletin Solutions, Inc.