Gauss Weapons, Reloaded!

Not going to lie. I want one!

I've long said that I was going to get around to tackling gauss weapons on this post and its about time I make good with my word!

In today's (late GURPSday) post I take a look over the gauss weapons in Ultra-Tech and see if I can give them a good dose of updating!











For the past couple of weeks the ol' Doctor of GURPS ballistics himself, Douglas Cole (actually a real doctor and has actually really been a ballistic object before), has been taking a crack at updating the rather dodgy assumptions and stats that conventional fire arms had in Ultra-Tech with a little feature he calls Sunday is Gunday (praise the lord and pass the ammo) over on his blog, Gaming Ballistic. 

Then there's the fact that not to long ago PK released this post over on the GURPS Forums were David was reevaluating how damage is handled with EM weapons.

Well, needless to say both of these factors inspired me to get back on track with messing around with gauss weapons. Now the last time I tackled gauss weapons was do to a request and I hadn't quite yet settled on way that tackled the subject to my satisfaction. While the stat I came up with aren't that off, they were based on  the stats from Ultra-Tech as is and well... these stats have issues.

And I don't mean like in the usual typos, typos everywhere! that Ultra-Tech is known  and loved for for (40mm railgun has a 150lbs magazine. Magazine holds 200 rounds. 40mm rounds weigh 6lbs per shot.... yeah seems legit).

First off, to quote David L Pulver himself, "Since the Weapon Design Rules, while functional, remain vaporware, some weapons in UT were not modified if deviated too much from Basic Set."

Basically the stats for the gauss weapons were based off of the gauss weapons found in the Basic Set and were basically made without any kind of real design process, this means that they do not line up at all with the more logically designed weapons that show up in High-Tech. Because of this while my write ups line up with Ultra-Tech, Ultra- Tech doesn't line up with later books.

So I figured that it was about time to finally through my weight in at this problem and see if I could do something about it. Now this isn't going to be a total breaking down and rebuilding of the assumptions behind the weapons that Doug is doing but rather an attempt to bring the weapons in line with the more evolved way of stating guns found in High-Tech as well as make the weapons all have a connecting logic rather then seemingly being stated up on a whim.

So to go over what I did:

For damage and range I used the formulas Douglas Cole derived for his custom spreadsheet His sheet is the closest thing we have to the raw figures atm though his figures for half damage range do seem to differ from RAW a little. Note as suggested by  the EM weapons update post,  the listed damage values are with the weapons fired standard, non-AP rounds. Upgrade the round to APEP to bring them back up to what's listed in Ultra-Tech (I also offer an alternative write up of APEP rounds at the end of this post).

Figuring muzzle energy and power draw was pretty easy.

The 4mm gauss rifle stated it fired at around 5,000fps (1,5000m/s actually) and the rounds weights 0.006lbs. This gives a muzzle energy of 3.07kJ. For the other 4mm gauss weapons I just had to scale the energy with the given ranges and damage. The 7mm HMG was a little trickier as the only listed velocity for the 7mm round is way over the top so I had to scale velocity to got I got something that lined up with listed damage.

The drained power per show was figured by taking a look at how much energy it would take to fire a full magazine for given gauss weapons and compering that with the energy density of TL10 power cells. This worked out to an efficiency of around 50%.

For weight I divided the listed empty weights of the weapons covered and divide them by their muzzle energy and then scaled them down to what they would weight if they had ROF 1. This of course resulted in a weight range that was kinda all over the place. While most of the 4mm gauss weapons were in the same ball park, the heavier weapons got really light for loads they were flinging.

After some messing around I found that an base empty weight of 1.81lbs×muzzle energy in kilo Joules. For weapons with ROF greater then 1 I multiplied the base empty weight by 1+(ROF/20). This gave me results that were pretty close across the board. Heavy weapons like the 7mm HMG and then 4mm minigun ended up much heavier then the listed weights but their official weights don't make any sense when compared to how heavy less powerful gauss weapons are.

Cost is pretty steady at $1,000 per pound of weapon weight.

Bulk was figured using the bulk formula from the Blaster and Laser Design System (Pyramid 3/37 Tech and Toys II). It's flawed but it does work pretty well for small arms (it does get wonky with larger weapons though).

For Rcl, I did test out some ideas I had for how the stat is figured but in the end they all gave me Rcl 2 anyway so I left Rcl as is. My Rcl ideas aren't ready to be published yet.

For ST, you guys can use this work around.

For magazines I added the power cells to them to make using the weapons simpler. I also made sure they had enough power cells to fire their entire magazines in boosted-velocity mode.

Weight of a loaded magazine was figured as the weight of ammo plus the weight of power cells times 1.1. Cost was figured as $15 plus five times the WPS of the ammo used plus the cost of the power cells. Note that I made no attempt to match up with the listed magazine weights since they're mostly crap heh.
For this post I am only going to be updating the 4mm and 7mm gauss weapons.

The reasons I'm not covering the other weapons in this post  are the following:

I quickly realized that needlers were terrible weapons so I skipped them.

Shotguns I'm skipping for now since I can't seem to make them work.

Starting with the funky ammo, the listed guass shotguns use the 18.5mm ammo which weighs less then half what a normal modern day slug does which even with boosting the muzzle velocity to 1.5 times higher then modern shotguns only ekes out around the same amount of damage rather then the 8d claimed. Also given its weight and diameter, it has to have the odd  aspect ratio of 0.5:1 which means that along with its light weight this round is going to bleed energy hard and have a crappy half damage range, in fact I calculate it at only 80 yards (though do to the higher velocity max range is increased)!

Then comes their weights. I peg the shotgun rounds as having a muzzle energy of around 4.6kJ or about 1.5 times higher then the gauss rifles. With this in mind the gauss CAW, which has a ROF of 15 only weighs 8.5lbs empty. Not too bad but definitely off when your realize that it only weighs 20% more then the gauss rifle despite its greater muzzle energy and higher ROF. Then there's gauss shotgun pistol which, admittedly, has a much lower ROF of only 3 but that doesn't explain why it only weighs 2.5lbs empty! Then there's the fact that the CAW costs only ~$282lbs per pound yet the gauss shotgun pistol costs $800 per pound (which still isn't bad since most gauss weapons seem to cost $1,000 per pound). Why do shotguns cost so little? Why does the shotgun pistol cost so much more then the CAW? I have no clue so I'm probably going to have to home rule the frak out these to make them make sense.

For the gauss grenade launchers, I had the same issues as with the shotguns. In order to get the 4d worth of damage that they are listed as doing required extremely high muzzle velocities and therefor really high muzzle energy and there was no way it made sense that they're were as lite as they are. Any grenade launcher stats I come up with are going to look nothing like what was published so I'm gonna tackle them later.

I haven't looked into gauss mortar launchers as hard as the other weapon yet so I'm gonna save them for later. 

Rail guns, like with shotguns and grenade launchers, were something I really wanted to include them with this write up but as far as I can tell how they are handled in the book is broken. They are clearly superior to gauss weapons and there is no reason why you would want to use this tech is rail guns can shoot as fast as the do with the muzzle energies that they do at the low weights and costs.

To give you an example, in the book the 4mm gauss LMG weighs 13lbs empty and has a muzzle energy of of 3.07 and has a ROF of 20. The 40mm railcannon also has a ROF of 20, would need a muzzle energy of the order of 3.5 mega Joules to do the listed damage and weighs 2 tons. This means for every kilo Joule the gauss LMG weighs about 4.2lbs while the the rail cannon weighs only 1.2lbs per kilo Joule. As you can see there are some clear issues here. Oh and to add insult to injury the rail gun costs less then $160 per pound while the LMG costs $1,000!

I'm still pondering what I should to do handle this dilemma and since any solution I come up with are going to be clearly in house rule department while I'm trying to at lest keep half a foot in regards to RAW with this I'm going to just hold off any solution I come up with for a future post where I tackle custom electromagnetic weapons.

Now on to the goods. 

 EM Ammo


4mm Gauss Round
The 4mm gauss round is  a 42 grain projectile (0.006lbs/0.0027kg) and has a 8:1 aspect ratio making the round 4×32mm. Given its weight and size, gauss rounds has and estimated density around 9.9g/cc which points to a round that has a tungsten core that is just shy of 20% of the rounds total weight and a steel body that makes up the other just over 80% (keep in mind this is just a guess however and it's possible it has a different composition). Do to its small diameter and long aspect ratio (which makes it very stable in flesh) the 4mm gauss round should only do small piercing damage despite PK's suggestion to make them full piercing damage. Cost per shot is still $0.06 but now this only covers standard "ball" ammo.

7mm Gauss Round
The 7mm round, at 168 grains (0.024lbs/0.011kg), needs to have an aspect ratio of 6:1  to weigh that much, making the round 7×42mm. This is a rather beefy round that sadly got almost no love in Ultra-Tech. I might make some custom 7mm weapons down the line. Unlike the 4mm gauss round, the 7mm gauss round is meaty enough that I think it aught to be counted as full normal piercing damage. Cost per shot is $0.24.


Gauss Weapons

Gauss Pistol, 4mm (TL10)
This one didn't have to change too much. Its empty weight went down slightly as a result of tweaking the math so that the weights of gauss weapons didn't get too crazy at either end of the spectrum. The magazine also lost 0.1lbs of weight do to using more update rules for designing magazines from High-Tech (pg. 155).


In order to line up with the listed weight and damage, it needs to fires at 625m/s with a muzzle energy of 0.53kJ and a power drain of 1.06kW per shot.

In boosted velocity mode velocity becomes 812.5m/s, damage increases to 4d-1 pi-, range to 800/4,300, muzzle energy jumps to 0.69kJ and power drain to 1.38kW per shot.

In low velocity mode, velocity drops to 312.5m/s, damage to 2d+1 pi-, range to 310/2,800, muzzle energy to 0.27kJ and power drain to 0.54kW per shot.

Powered by two B cells built into the magazine which provide enough energy to fire the full magazine in boosted-velocity mode.

The power supply of the Gauss Pistol is robust enough to handle Fast-Firing (High-Tech pg. 84) and can be modified to have a ROF of 10 with simple 10 min Armory (Small Arms ) roll.

Gauss Machine Pistol, 4mm (TL10)
Pretty much the same as the regular Gauss Pistol but with a heavy automatic generator letting it fire with ROF 20.

Powered by two B cells built into the magazine which provide enough energy to fire the full magazine in boosted-velocity mode. 

A 80 round extended magazine  would weigh 0.7lbs, costs $29, increases ST to 10, worsens bulk to -3 and is powered by 4 B cells.


Gauss PDW, 4mm (TL10)
Like with the gauss pistol, the PDW lined up pretty well only weighing slightly less then the published version. 

It shoots at 875m/s  with a muzzle energy of 1.04kJ and a power drain of  2.08kW per shot.

In boosted velocity mode velocity becomes 1,137.5m/s, damage increases to 5d+1 pi-, range to 800/5,000, muzzle energy jumps to 1.35kJ and power drain to 2.7kW per shot.

In low velocity mode, velocity drops to 437.5m/s, damage to 3d+1 pi-, range to 320/3,300, muzzle energy to 0.52kJ and power drain to 0.4kW per shot.

Powered by four B cells built into the magazine which provide enough energy to fire the full magazine in boosted-velocity mode.


Gauss Rifle, 4mm (TL10)
This version of the 4mm gauss rifle comes in a little heavier, there was just no way to make this line up with the listed weight and also line up close with the weights of the other gauss guns.

Since its heavier its bulk went up a notch, making it on par with a full sized rifle rather then a carbine sized one. Because of this I also bumped up is Acc to match.



It fires a projectile at 1,500m/s with a muzzle energy of 3.07kJ and a power drain of  6.14kW per shot.

In boosted velocity mode velocity becomes 1,950m/s, damage increases to 9d+1 pi-, range to 800/6,300, muzzle energy jumps to 3.99kJ and power drain to 7.98kW per shot.

In low velocity mode, velocity drops to 750m/s, damage to 6d-1 pi-, range to 320/4,200, muzzle energy to 1.54kJ and power drain to 3.08kW per shot.

Powered by two C cells built into the magazine which provide enough energy to fire the full magazine in boosted-velocity mode.


Gauss LMG, 4mm (TL10)
Basically the 4mm gauss rifle with a heavy automatic generator and a heavier barrel. Its a bit heavier for the same reasons the gauss rifle are.Weight includes a built in bi-pod.

If you are using the more detailed Sustained Fire rules found on pg 84-85 of High-Tech, the gauss LMG can sustain fire for 1,800 rounds, rapid fire for 900 rounds, and assault fire for 450 rounds. 

Powered by 7 C cells built into the magazine which provides enough power to fire the full 300 rounds in boosted-velocity mode.

Gauss HMG, 7mm (TL10)
First thing that needs to be addressed here is that the flavor text for the listed version is in error and according to the word of David should read:

Gauss Heavy Machine Gun (HMG), 7mm (TL10): This is a tripod-mounted infantry support weapon. It fires the same round as the sniper railgun, at a lower velocity and higher rate of fire.

The mentioned of using the same round as the 4mm gauss rifle should be ignored. 

I had to do some work with this one since it seems that its stats were based on a scaled up, rapid fire version of the TL9 7mm sniper rifle. This is a problem since Ultra-Tech states that rail guns are more powerful for a given size but have a slower rate of fire. This means that the gauss HMG as stated has the rapid fire ability of a gauss weapons by the muzzle energy of a rail gun....

So for my version, since I had to kinda discount the whole idea as stated, I just went for a version that weighed in close to the gauss minigun so that they at lest some what lined up with their the official versions. Incidentally this gave me 16d worth of damage.

On a side note, since I'm not covering rail guns in this write up I should at lest  point out that there is no way in hell the 7mm sniper railgun has a muzzle velocity of 10,000fps! This would give it a muzzle energy of over 49kJ and give it almost 29d of damage! And given that the sniper rail gun only weighs 18lbs even at TL9 this would make rail guns even more broken then they already are! Also given the gauss HMG stats, this would mean that that it would of had a muzzle velocity of 12,500fps. A more realistic muzzle velocity of the sniper railgun is 5,250fps.

The gauss HMG fires at 1,700m/s with a muzzle energy of 15.76kJ and a power drain of 31.52kW.

In boosted velocity -mode its muzzle velocity increases to 2,210m/s and energy to 20.49 and power to 40.98kW. Damage increases to 18d+1 pi and range increases to 1,020/8,400.

In low velocity mode, velocity drops to 850, energy drops to 7.88kJ and power drops to 15.76kW. Damage becomes 11d+1 pi and range becomes 410/5,600.

If you are using the more detailed Sustained Fire rules found on pg 84-85 of High-Tech, the gauss HMG can sustain fire for 1,800 rounds, rapid fire for 900 rounds, and assault fire for 450 rounds.   

Powered by 3 D cells located in the magazine which provided enough power to all 200 rounds at boosted velocity.


Gauss Minigun, 4mm (TL10)
As with the gauss rifle, the weight of the minigun got shot up a bit. Also there's no way the magazine weighs only 20lbs when it has a 20lbs power cell plus 6lbs of ammo.

To keep the weight reasonable I reduced the ROF to 66 and made it a three barreled design. Note that the ROF doesn't have a ! after it, the guass minigun can set to fire at any ROF the gunner wants up to the max of 66 but the gunner needs to a ready action to set the number of rounds that will be fired per trigger pull. If not preset then treat it as have a ROF of 66!.

It fires at 2,250m/s with a muzzle energy of 6.9kJ and a power drain of  13.8kW per shot. The 4mm gauss minigun uses a three barreled gatling action and requires 2.6kW of power.

In boosted velocity mode velocity becomes 2,925m/s, damage increases to 14d+1 pi-, range to 800/7,500, muzzle energy jumps to 8.97kJ and power drain to 17.94kW per shot.

In low velocity mode, velocity drops to 750m/s, damage to 8d+2 pi-, range to 320/5,000, muzzle energy to  3.45kJ and power drain to 6.9kW per shot.

If you are using the more detailed Sustained Fire rules found on pg 84-85 of High-Tech, the gauss minigun can sustain fire for 3,600 rounds, rapid fire for 1,800 rounds, and assault fire for 900 rounds.

Powered by a D cells built into the magazine which provide enough energy to fire the full magazine in boosted-velocity mode as well as to power its gatling action. 



GUNS (PISTOL) (DX-4, or most other Guns at -2) 
TL Weapon                                  Damage      Acc      Range        Wt.          ROF     Shots   ST   Bulk   Rcl. Cost            LC
10 Gauss Pistol, 4mm                   3d+1 pi-      3         660/3,800    1.8/0.4     3        40(3)     8      -2        2     $1,400/$22   3
10 Gauss Machine Pistol, 4mm    3d+1 pi-      3        660/3,800     2.3/0.4    20       40(3)     9     -2         2     $1,900/$22   3 


GUNS (SMG) (DX-4, or most other Guns at -2)
TL Weapon                    Damage  Acc     Range        Wt.      ROF   Shots   ST   Bulk Rcl. Cost               LC
10 Gauss PDW, 4mm    5d-1 pi-    5+1    660/4,500   4.5/1   16       80(3)    7†    -3      2     $3,400/$27     2


GUNS (RIFLE) (DX-4, or most other Guns at -2)
TL Weapon                   Damage  Acc     Range       Wt.          ROF   Shots   ST  Bulk Rcl. Cost           LC 
10 Gauss Rifle, 4mm    8d+1 pi-   6 +2   670/5,600 10.4/1.5   12        60(3)    9†  -5       2    $8,900/$37   2


GUNS (SHOTGUN) (DX-4, or most other Guns at -2)
TL Weapon                       Damage  Acc     Range       Wt.          ROF   Shots   ST  Bulk Rcl. Cost           LC 
10 Gauss CAW, 18.5mm    6d+1 pi++   5   80/1,400      16.4/1.8   15        30(3)   10†  -6       2    $15,000/$31   2



GUNS (LMG) (DX-4, or most other Guns at -2)
TL Weapon                   Damage  Acc     Range       Wt.          ROF   Shots    ST      Bulk  Rcl. Cost             LC  
10 Gauss LMG, 4mm   8d+1 pi-  7 +2   670/5,600  21.7/5.8    20        300(5)  11B†   -7       2     $14,000/$94  2


GUNNER (MACHINE GUN) (DX-4, or other Gunner at -4)
TL Weapon                      Damage     Acc     Range       Wt.          ROF   Shots       ST       Bulk   Rcl.   Cost               LC  
 10 Gauss HMG, 7mm    8d×2 pi-       8       850/7500   93.1/21.8    20     200(5)       20M  -12      2     $71,000/$340   1 
10 Gauss Minigun, 4mm  12d+2 pi-   8       660/6,700   103/39     66        1,000(5)  20M  -12    2     $73,000/$2,050    1  


The rules for APEP were based off of the stats for ammunition upgrades featured in the Basic Set and therefor do not line up with the better written rules found in High-Tech. Below I offer an alternative write up for APEP rounds that bring them inline with High-Tech. I also found that it was odd that APEP costed so much, as much as TL11^ hyper dense rounds do. I adjusted the cost to be a step more expensive then DU rounds (which are actually pretty cheap since DU is a waste product) and the cost of APHD rounds.

Armor-Piercing Enhanced Penetratior (APEP) (TL9)
An APDS round with a core made of tungsten-reinforced bulk amorphous metal. This provides equivalent or superior performance to depleted uranium without toxic residue. Add an armor divisor of (2). Multiply damage by 1.7. If caliber is below 40mm, reduce damage type: Pi++ becomes Pi+, Pi+ becomes Pi, Pi becomes Pi-, and has no effect on Pi-. Double range. Not available for grenades or mines. Multiply CPS by 7.