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Old 09-26-2017, 03:15 PM   #51
hal
 
Join Date: Aug 2004
Location: Buffalo, New York
Default Re: GURPS ULTRATECH ballistics?

Finally Finished Modifying Doug's Original Ballistic spreadsheet for my purpose. I've done away with Doug's original set up listing Chamber Pressure, Barrel bore, Case Length, Chamber Bore, Barrel length, Bullet Mass, Aspect Ratio, Burn length, Projectile Caliber, and Total Accelerated Mass.

Instead, I'm using:

Bullet Mass, Bullet Mass in Grams, Velocity in Feet/sec,
Velocity in Meters/Sec, Kinetic Energy in Joules, Average Bullet Damage, GURPS Dam, Bullet Xsecton, Half Damage Range, Max Damage Range, Sectional Density, Loss Coefficient, Aspect Ratio, and Projectile Caliber

Bullet Mass in Grams is just a calculated conversion from Grains, it is only used for reference comparison (such as when someone talks in Grams and someone else talks in Grains), Kinetic Energy in Joules (Also for reference, not directly necessary in the calculations). All other values are used for calculations as necessary.

Here is a sample gun written up based on Greenhill Military Small Arms Data Book.

Code:
Bullet Mass in grains	193	
Bullet Mass in Grams	12.50618963	
Estimated Bullet Length	20.8 based on aspect ratio	
Velocity in Feet/sec	725	
Velocity in Meters/Sec	220.98	
Kinetic Energy/Joules	305.35	
AverageBullet Damage	6.4	
GURPS Dam	        2D-1	
Bullet Xsecton	        0.00008495	
Half Damage Range	313	
Max Damage Range	1157	
Sectional Density	0.147243056	
Loss Coefficient	0.002116065	
Aspect Ratio	2	L/Bore
Projectile Caliber	10.4mm
		
		
Name	Troopers M1878	
Cartridge	10.4x20R Swiss Ordinance	
Length	9.25 Inches	
Weight	1.625 lbs	
Magazine	6 Round Cylinder	
Muzzle Velocity	725 Feet per second	
		
Cartridge	10.4x20R Swiss Ordinance	
Bullet Weight in Grains	193
Note, I don't have access to the aspect ratio, but it appears that the aspect ratio should be around 1.8 to 2.1 (or about 2.0 for pistol rounds), and about 3 to 5 to 1 for Rifle bullets. For my own use, I'd have to guess as best as I can where I can.

As for using this with other game systems? For those who have GUNS GUNS GUNS by Greg Porter, it has rules for designing your own cartridges along with guns. At the very least, it can be used for making your own "Sci-fi" weapons to some extent. Is it 100% compatible with GURPS? Not really in the sense of damage values or anything else. But it does give you the tools to build your cartridges or weapon systems, assign real world values for weight, etc - and guidelines for stats for GURPS 3e rules - which should be enough to make these guns usable for GURPS 4e.

As long as you have the velocity in feet per second, the bullet weight in Grains, the Diameter of the bullet, and the Aspect ratio - the spreadsheet will give you some basis for what the designed weapon system should be for use with GURPS 4e.

The Next time I post to this thread with a weapon design, I will try and design a Sci-Fi type gun without using Caseless or anything else - just conventional rounds in an unconventional diameter etc - just to see what I can create.

Note: this does not calculate Weapon Accuracy based on barrel length, nor unconsumed propellants or what have you. All it does is give you damage, half/damage range, and Max Damage range. It is already known to produce results not in synch with GURPS HIGH GUARD, but it seems to do the job until such a time as someone publishes a Pyramid Article for designing conventional guns for use with GURPS 4e like they did with the Energy guns.

What might prove to be interesting is to see if the GGG rules (now called 3G3 if you buy the PDF version) can create a credible Caseless Round and stats for it, such that I might be willing to compare/contrast it against ULTRATECH's values. Might prove to be interesting.

:)
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Old 09-26-2017, 07:18 PM   #52
mlangsdorf
 
Join Date: Aug 2004
Location: Austin, TX
Default Re: GURPS ULTRATECH ballistics?

Quote:
Originally Posted by hal View Post
Note: this does not calculate Weapon Accuracy based on barrel length, nor unconsumed propellants or what have you. All it does is give you damage, half/damage range, and Max Damage range.
So I have a slightly more advanced/crazy spreadsheet here:
https://docs.google.com/spreadsheets...it?usp=sharing

which is a mix of Doug's spreadsheet, GURPS Vehicles (2nd ed) for 3e, and 3G3, with a dash of whatever data I can get off the web. It will give weapon damage, accuracy, weight, weight per shot, and costs. It's usually accurate to within +/-20%, except for cost, which is generally a best guess. Not all stats will match GURPS stats, either.

One big friction point is Doug's calculator uses chamber pressure, chamber volume, and burn distance to calculate kinetic energy, and for a lot of historic and imaginary guns, its hard/impossible to get those values. I'm using modified 3G3 propellant energy to estimate those values, but the 3G3 formula for estimating barrel length is extremely bogus. Anyway, I'm sticking it out there for people to look at.

Quote:
What might prove to be interesting is to see if the GGG rules (now called 3G3 if you buy the PDF version) can create a credible Caseless Round and stats for it, such that I might be willing to compare/contrast it against ULTRATECH's values. Might prove to be interesting.
In principle, 3G3 can create caseless rounds/weapons, and a caseless round should do the same amount of damage as a cased weapon with the same weight, cross-section, and muzzle velocity.
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Old 09-26-2017, 09:14 PM   #53
hal
 
Join Date: Aug 2004
Location: Buffalo, New York
Default Re: GURPS ULTRATECH ballistics?

Quote:
Originally Posted by mlangsdorf View Post
So I have a slightly more advanced/crazy spreadsheet here:
https://docs.google.com/spreadsheets...it?usp=sharing

which is a mix of Doug's spreadsheet, GURPS Vehicles (2nd ed) for 3e, and 3G3, with a dash of whatever data I can get off the web. It will give weapon damage, accuracy, weight, weight per shot, and costs. It's usually accurate to within +/-20%, except for cost, which is generally a best guess. Not all stats will match GURPS stats, either.

One big friction point is Doug's calculator uses chamber pressure, chamber volume, and burn distance to calculate kinetic energy, and for a lot of historic and imaginary guns, its hard/impossible to get those values. I'm using modified 3G3 propellant energy to estimate those values, but the 3G3 formula for estimating barrel length is extremely bogus. Anyway, I'm sticking it out there for people to look at.



In principle, 3G3 can create caseless rounds/weapons, and a caseless round should do the same amount of damage as a cased weapon with the same weight, cross-section, and muzzle velocity.
Thanks Guy. I just wondered whether or not the Caseless rounds would bear any resemblance to the "caseless ammo tend to be 1/2 the weight of conventional cartridges" or not.

I'll never forget the day when I spent time working on the M-4 Cohen Main Battle Tank using GURPS VEHICLES that was designed to use a Rail gun. When I saw the damage it was capable of inflicting, It became VERY difficult to create a frontal armor level that could handle its own gun. But then I integrated it with a squad of battle suits with a central networked computer aboard the tank, and used Gatling 4mm rounds for both offensive weaponry and "anti-missile" point defense for the tank. It was fun, and I miss the days of GURPS VEHICLES 2nd edition. :(

Even started up a wargame based on Columbia where the US landed the US Marine Expeditionary Force aboard hovercrafts and landed their heavy main battle tanks for fire support. Game never progressed very far alas. :(

While I don't much like the hit point values with the newer GURPS 4e rules set, I still miss the Vehicle Design rules and wish they'd publish the darn thing, even if it were to be published in parts or installments instead of one whole entire book like GURPS VEHICLES 2nd edition was.
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Old 09-27-2017, 07:17 AM   #54
mlangsdorf
 
Join Date: Aug 2004
Location: Austin, TX
Default Re: GURPS ULTRATECH ballistics?

For rifle caliber bullets, 3G3 suggests roughly a 3:1:3 ratio of bullet mass to propellant mass to casing mass. A caseless round should weigh about 4/7ths an equivalent cased round - and when you consider that you're really evaluating TL6 cased rounds with moderate REF propellants versus TL8+ caseless rounds with higher REF propellants, you can get half the weight.

I can recreate the UT 10mm CLP pistol - one solution is a 10mm bullet, aspect 2, density 4.5 (which is fairly low - real bullets are usually around 7-10) for a bullet mass of 5.3 grams. Using ~14 grams of propellant at 43 kPSI and 5.5mm of burn distance, you end up with a velocity of 530 m/s and 3d pi+ damage, 1/2 ~150 yds, max ~1800. More reasonably you can use a density 7 bullets with the same propellant for a velocity of 425 m/s, same damage, and 1/2d 200 yds and max ~2200 yds, but then weight per shot jumps to 0.021. .40 S&W weighs 0.035 per shot, so you're in the ballpark of "half the weight of conventional cartridges."
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Old 09-27-2017, 10:35 AM   #55
Anthony
 
Join Date: Feb 2005
Location: Berkeley, CA
Default Re: GURPS ULTRATECH ballistics?

Realistically, I suspect case weight is more a function of propellant weight than projectile weight. If you've got a 4g bullet with 1.5g powder (5.56mm), the powder is something like three times the volume of the bullet and is enclosed completely while the bullet is only partially enclosed, so ~90% of the case volume is for powder. On the other hand, if you've got a 7.5g bullet with 0.3 grams of powder (9mm), something like 40% of the case is for powder, and it's at lower pressure so the case walls can be thinner.
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Old 09-27-2017, 11:25 AM   #56
hal
 
Join Date: Aug 2004
Location: Buffalo, New York
Default Re: GURPS ULTRATECH ballistics?

Based on reading online for reloading bullets and the like, part of the purpose of the brass casings for bullets was to act as a heat sink for the gun in an effort to keep it cool enough to fire (not the primary consideration to be sure!). Then there are those cartridge case designers who wish to insure that the cartridge with one design spec and would be dangerous to place in a pistol due to over pressurization effects - are deliberately made longer or what have you to insure that the rounds can't be placed in guns that it would be dangerous for.

3G3 (or Guns Guns Guns) made a point for designing your own weapon systems and even of cartridges, but I'm finding it maddening right now to incorporate something as simple as "bullet volume" and "Bullet Mass" simply because the formula required to determine volume was never listed in the book form or the PDF form of the material. When I use actual volumes for spheres, I can make my data match the tables given in the book (1:1 aspect ratio). However, when I attempt to create a formula that handles the 2:1 or higher aspect ratios, that is when I find my formula produces results that don't match the table. After all these years, I've NEVER noticed that bit of information.

According to the book form, which states that the volumes are based on Hemisphere plus cylinder volumes - simply halving the volume of a sphere will produce a hemisphere. Knowing that the Length to diameter ratio is supposed to be 2 to 1 gives me some means for estimating the height of the bullet as being equal to Aspect ratio x Diameter minus 1/2 diameter (for the hemisphere aspect). So, the formula for the volume would simply be 4/3 * R^3 * Pi all divided by 2 (for the hemisphere) plus 1/2 Diameter * R^2 x Height for the Cylinder.

I did find online, a program written in basic that estimates the volume of a rifle bullet that was boat tailed, squared bottom or other such - which if I can translate into VB.NET code, will probably work out nicer for getting better bullet masses or volumes than the GGG rules, but that's something else for a rainy day (for now). So, do I trust GGG 100% Not entirely. It is however, better than nothing - and we can't use GURPS VEHICLES 2nd edition rules for designing guns for use with 4e per se - but at least, for me, it keeps my mind occupied and out of trouble. ;)
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Old 09-27-2017, 12:01 PM   #57
Fred Brackin
 
Join Date: Aug 2007
Default Re: GURPS ULTRATECH ballistics?

Quote:
Originally Posted by hal View Post
Based on reading online for reloading bullets and the like, part of the purpose of the brass casings for bullets was to act as a heat sink for the gun in an effort to keep it cool enough to fire
"Purpose" implies deliberate design from the outset. "Useful side effect discovered later" is far more likely.
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Old 09-27-2017, 02:06 PM   #58
mlangsdorf
 
Join Date: Aug 2004
Location: Austin, TX
Default Re: GURPS ULTRATECH ballistics?

Quote:
Originally Posted by hal View Post
According to the book form, which states that the volumes are based on Hemisphere plus cylinder volumes - simply halving the volume of a sphere will produce a hemisphere. Knowing that the Length to diameter ratio is supposed to be 2 to 1 gives me some means for estimating the height of the bullet as being equal to Aspect ratio x Diameter minus 1/2 diameter (for the hemisphere aspect). So, the formula for the volume would simply be 4/3 * R^3 * Pi all divided by 2 (for the hemisphere) plus 1/2 Diameter * R^2 x Height for the Cylinder.
I stole this from Doug's spreadsheet:
volume in cubic cm = (PI*(Bore/2)^3 + PI/12*Bore^2*(2*Bore*Aspect Ratio-Bore)) / 1000

where bore is bullet bore in milliimeters and aspect ratio is bullet length / bullet bore.

It doesn't match the G3G numbers, but it doesn't have any discontinuities and its's pretty close.

Bullet volume and density are very much a best guess in my opinion - it's hard to get precise data especially as you move into the past. Some things are really well documented, some things aren't, and sources don't always agree with each other. If you've got a formula that works, go with it.

You can use Vehicles 2nd ed rules to make guns for GURPS4e, if you're willing to work out how the numbers change. Personally, I found the Vehicles 2e rules to be a little vague, hence my spreadsheet upthread.
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Old 09-27-2017, 04:36 PM   #59
hal
 
Join Date: Aug 2004
Location: Buffalo, New York
Default Re: GURPS ULTRATECH ballistics?

Anyone know what this means by chance? I had access to a Google Docs file and downloaded it as an XLS file, got this result:

"Removed Records: Formula from /xl/worksheets/sheet1.xml part"

On to other things...

I got this from a Ballistics web page that included the program in Basic from about the late 1980's for determining the volume of a rifle bullet.


Code:
 
LEAD	                                  11.34
COPPER	                                   8.89
BRONZE	                                   8.78
BRASS	                                8.2 to 8.6
LINOTYPE	                          10.4
JACKETED SOFT POINT	               10.25 to 10.4
JACKETED HOLLOW POINT        	       10.0 to 10.11

Last edited by hal; 09-27-2017 at 05:12 PM.
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Old 09-27-2017, 04:37 PM   #60
hal
 
Join Date: Aug 2004
Location: Buffalo, New York
Default Re: GURPS ULTRATECH ballistics?

Quote:
Originally Posted by mlangsdorf View Post
I stole this from Doug's spreadsheet:
volume in cubic cm = (PI*(Bore/2)^3 + PI/12*Bore^2*(2*Bore*Aspect Ratio-Bore)) / 1000

where bore is bullet bore in milliimeters and aspect ratio is bullet length / bullet bore.

It doesn't match the G3G numbers, but it doesn't have any discontinuities and its's pretty close.
Thanks for this. :)

Added thought: it occurs to me, that if you have weight of bullet and density of bullet, that volume of bullet can be determined, and that once you have volume, the aspect ratio can be estimated based on that. Doubly thanks to you and Doug for that.

Last edited by hal; 09-27-2017 at 05:09 PM. Reason: Added thought
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