From: "David L. Pulver" <[email-masked]>

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GURPS Vehicles 2: TL6+ Weaponry Expansion
     This article offers rules variants for building additional 
weapons with GURPS Vehicles 2nd Edition. I have borrowed (and
heavily modified) some of Doc Kromm's ideas for this. Comments
are welcomed, but should also be sent via email to me
([email-masked]) if you want to ensure I read them.
     Please note that these rules are very rough and may well
contain errors, and that this article is in no way official,
though I may later submit something like it to Pyramid later.
 
Gun Technology: Gas-Powered Guns (TL7)
     These guns are powered by a compressed gas cartridge,
sometimes in conjunction with a spring. The gas cartridge store
is assumed to be included with their ammunition weight. Their
main advantage is that they produce no sound or heat and use no
power cells. Needlers (p. UT50) are an example.   A gas-powered
gun uses the normal design system, with these modifications:
     Type and Damage: G is 0.75.
     1/2D Range: G is 0.75.
     Weight: Treat weapon an electromag gun except that T is 2 at
TL7.
     WPS, VPS: As "other conventional gun."
     CPS: As electromag gun.
     Power: As conventional gun.
     Cost: As conventional gun, but double cost.
 
Hand-Held Weapon Design: Variant Rules
     These optional rules alter the rules slightly to permit more
realistic handheld weapon design.
     *Launcher Design:* When calculating the empty weight of a
launcher with a rated maximum load under one pound, base mWPS on
the *square root* of the WPS, rather than the WPS itself.
     *Min. Grip Weight:* If a weapon weighs under 2.5 pounds, a
longer shoulder stock is needed so that the weapon can reach the
shoulder. Instead of a shoulder stock multiplying empty weight by
1.2 (1.5 if bipod) it adds 0.5 pounds to weight (1.25 lbs. if
bipod). These numbers may vary for non-humans that have bigger or
smaller hands: optionally, multiply them by racial average ST/10.
     *Light Tripod:* This can be used instead of a normal tripod.
It weighs only half the weapon's empty weight. It is more
expensive, costing $30 per pound that the tripod weighs.
     *Powerpacks:* A weapon that uses D or E cells can mount them
in a backpack, instead of increasing the loaded weight of the
weapon. The powerpack (empty) and heavy-duty power cable together
weigh 20% of the weight and cost of a D or E cells, but do not
increase the weapon's loaded weight. This is a good way to keep a
weapon's ST and SS requirement low. But replacing power cells
takes at least twice as long, unless someone else assists the
user. A weapon that is plugged into a powerpack cannot be
concealed; unplugging or plugging in the weapon takes at least
two seconds.
 
New Statistic: Holdout
     A weapon's Holdout modifier is calculated using this table
and the weapon's empty weight. If a weight falls between two
numbers, use the higher. If over 15 pounds, it cannot be hidden.
 
     0.05 pounds . . . . +5
     0.1 pounds . . . . +4
     0.2 pounds . . . . +3
     0.5 pounds . . . . +2
     1 pound . . . . +1
     1.5 pounds . . . . 0
     2 pounds . . . . -1
     3 pounds . . . . -2
     4.5 pounds . . . . -3
     7 pounds . . . . -4
     10 pounds . . . . -5
 
     Modifiers: if barrel is extremely short or very short: +1.
If barrel is long, very long or extremely long: -1. If weapon has
shoulder stock, with or without bipod: -1. Hand Grenade: -1.

Hand-Held Weapons: Design Options
     These design options can be added to a hand-held weapon
*after* all modifications described in the Hand-Held Weapons
sidebars (p. VE123-126) have been applied to its statistics.
     Some of these options require certain prerequisites.
 
Bullpup
     A bullpup weapon's breech and action are located behind the
trigger grip, reducing the overall length of the weapon. This has
the effect of making the weapon shorter, lighter, better-balanced
and easier to control *without* the need to reduce its barrel
length. However, a bullpup weapon has greater overall cost, and
is slightly less accurate than a conventional weapon.
     *Prerequisites:* TL7, Gun with Shoulder Stock.
     *Modified Statistics:* Acc -1, SS -1, Wt. -10%, ST -1,
Holdout -1, Cost +25%.
 
Double-Action or Single Action Automatic
     A late TL6+ fast autoloading smallarm may be either single
or double action, at the designer's option. See HT, p. 64.
 
Collapsible Weapon
     A weapon can be designed to fold up into a compact shape.
A folded weapon is effectively +2 to Holdout skill and sometimes
may not be recognized *as* a weapon. A fold-up weapon cannot be
fired while folded. It takes two seconds to unfold a ready folded
weapon into a firing position. If the weapon weighs more pounds
than the user's ST, it takes twice as long to do this. Folding up
the weapon takes just as long. To fold up a belt-fed machine gun
or weapon with a backpack power unit the belt or pack must first
!zqzbe removed.
     *Prerequisites:* TL6.
p&aCP0~     *Modified Statistics:* Add 20% to the weight and 100% to
cost of a weapon to make it folding, and +1 to SS due to its
extra bulk.
 
Folding Stock
     The weapon has a wire folding stock. When the stock is
folded, the weapon is more compact but harder to control.
     *Prerequisites:* Late TL6, Shoulder Stock.
     *Modified Statistics:* Empty weight -10%, Cost +10%. When
stock is folded, double recoil but add +2 to Holdout.
(Optionally, also reduce weapon's Acc by 3 and add +2 to its SS
number).
 
Quickdraw
     The weapon is designed to be small and light, with no
protruding parts that can catch on clothing or a holster.
Effective sights are often sacrificed, reducing accuracy. 
     *Prerequisites:* TL6, weapon must have pistol grip and
Holdout 0 or less.
     *Modified Statistics:* -1 Acc (min 0). Cost +20%. Gun adds a
+1 bonus to Fast-Draw skill.
 
Recoil Reduction
     This option adds a long muzzle-brake, special shock-
absorbing butt stock, extra springs or the like to reduce felt
recoil and thus lower both the recoil and ST requirement of the
weapon.
     *Prerequisites:* TL6, must have recoil -1 or more.
     *Modified Statistics:* Rcl -1. ST x 0.8. Empty Wt. +10%.
Cost +50%.
 
Sniper Guns
     These are built like ordinary weapons, but should normally
be fine or very fine (p. VE100) and equipped with sighting
devices (p. VE127).
 
Stealthed Guns
     A handheld weapon can be fitted with basic stealth, emission
or infrared cloaking to make it harder to detect. Find the volume
of the gun (as empty weight/50) and use that to determine surface
area. Use the table on p. VE92 to find the extra weight and cost
of stealth. This does not affect any other statistics.
 
Under Barrel Attachment
     The weapon is designed to be clamped beneath the barrel of a
weapon with a shoulder stock. This cancels most of the accuracy
penalty for lacking a shoulder stock, although not all since the
clamp mounting is not quite as solid as a shoulder stock.
     In a given turn a shooter can fire either the under barrel
or the above barrel weapon, or, if he uses both hands and fires
them at the same target, he can use both weapons. If firing both
weapons at once, add their recoil together.
     The most common type of under barrel weapon is a grenade
launcher attachment for an assault rifle.
     *Prerequisites:* Empty weight must be no more than 75% empty
weight of weapon it is mounted under. It must have Pistol Grip.
     *Modified Statistics:* Accuracy +2. If SS is lower than
mount weapon, increase it to the mount's SS. Its ST becomes
(combined ST of both weapons)/2. If it has recoil -2 or more,
reduce recoil by 1.
     If the weapon can only be fired while clamped under barrel,
there is no extra cost. Otherwise it is +10% to weight and cost,
and can be fired as a normal pistol (when doing so, use its
original stats, not the modified statistics described above).
 
Ultra-Tech Modifications
     See p. UT64 for other useful options.

Hand Grenades
     A hand grenade is built just like an iron bomb -- that is,
as a missile with no motor or guidance system. A grenade may use
any Explosive-type ammunition (not Kinetic/Explosive) or CHEM.One
sized for use by a human is normally 20mm to 60mm bore; a typical
20th-Century grenade is 40-60mm with normal or modest HE warhead.
     TL6-7 grenades are normally built with a 1 to 5 second fuse
delay (depending on the model), with HEDP, HESH or HEAT being
impact-fused. TL8+ grenades have an electronic fuse whose delay
can be set from impact to 5 seconds, taking one turn to change.
Arming a grenade takes one turn. Rules for using grenades are in
the Basic Set and in Space, Ultra-Tech, etc.
     *Stick Grenades:* A grenade may have a hand-grip to aid
throwing, like a WWII German "potato masher." Add 0.5 lbs. or
multiply by 1.2 (whichever is more) to weight, but give +2 to
Throwing skill when figuring distance. Extra weight may reduce
Holdout.
     *Plastic Grenades:* At TL7+ a hand grenade with HEC, HESH or
CHEM warhead may be made of plastic so it can slip past metal
detectors. Double the grenade's cost.
     *TL8+ electromag/hand grenades:* A 20mm to 60mm bore round
for an extra-low or low powered electromag weapon may be built to
also function as a hand grenade. Double the round's CPS.
 
Rifle Grenades
     These are launched grenades that are manually fitted over
the muzzle of any gun. They are propelled by firing a bullet into
a trap in the base of the grenade. No modification to the firing
weapon is required; the grenade is simply a special type of ammo.
     A rifle grenade may have a bore size of 20mm or more,
usually 20mm to 40mm. The grenade must be designed to be fired by
a range of bore sizes no more than 3mm apart, e.g., 5mm to 8mm.
The rifle grenade may not have a weight greater than the firing
weapon's; usually it is much less.
     Build a rifle grenade like a hand grenade, above. It can
only be used when launched from a gun firing solid ammunition.
     Aside from its type, damage, weight and cost, it has these
statistics when launched:
     SS: 18 or firing weapon's, whichever is greater.
     RoF: 1/6.
     1/2D: Equal to firing weapon 1/2D range times firing weapon
bore size divided by <I>four times<I> grenade's bore size.
     Max: Twice 1/2D range.
     Acc: Based on 1/2D range.
     Rifle grenades may be given rocket assist (p. VE112). All
modifiers apply after the above statistics have been calculated.
 
Extra Ammunition Types
     These types of ammunition are also available:
 
*New Ammunition*
*TL  Class*
     *Kinetic Energy*         
6##  HVS -- a tiny high-velocity spheroid.
8##  HD Needles -- a high-density needle built to pierce armor.
     *Energy Burst*
9@   Warbler -- a sonic noisemaker warhead.
16@  Stasis -- a stasis bomb warhead.
15@  Implosion -- an implosion bomb warhead.
 
     ## Only available for smallarms of under 2mm bore size. AP
needles may not be drugged or poisoned.
     @ Minimum bore size is 40mm.
     @@ Minimum bore size is 135mm at TL15, 40mm at TL16.
     Note that normal, but not HD, needle ammunition may be
drugged, as per p. UT50.
 
Ammunition Table
Ammunition     Type Damage    Rng       WPS  CPS       Acc
HVS            Cr.  0.66xKE   x0.066    /2!  x2        --
HD Needle      Imp. 0.5xKE(2) x0.66     --   x5        --
Warbler        Spcl (BxB)/50  x1        /1.5 x6        --
Stasis         Spcl (BxB)/833 x1        /1.5 x125      --
Implosion      Spcl (BxV)     x1        /1.5 x250      --
 
     *HVS*: ! Volume per shot is halved along with WPS.
     *Warbler:* Use the statistics on p. UT68, except that radius
of effect in yards is calculated using the damage formula above
Out to 5 x radius of effect, normal conversation is impossible.
     *Stasis:* Use the Stasis Bomb statistics on p. UT68 except
for area of effect in yards, which is calculated using the damage
formula above, and the fact that the weapon is impact detonated.
     *Implosion:* Use the Implosion bomb statistics on p. UT69
except that primary radius of effect (total destruction) is
calculated using the damage formula above. Out to twice this
radius damage is 20d, dropping to 10d at three times the primary
radius and 5d at four times the primary radius.
     *HD Needles:* Unlike other such rounds, HD needles do *not*
halve damage after penetrating DR. However, their base damage is
lower.    
     
Missile Warheads
     Warbler and stasis warheads are also usable on missiles of
40mm or larger diameter. Cost is as follows:
     x $50 if warbler.
     x $1,000 if stasis.
     x $2,000 if implosion.