A remote electroshock stun (or RES) gun uses a pair of ionization channels produced by ultraviolet laser light as a conductor for an electric current which shorts across the target. The electrical discharge has a pulse shape chosen to mimic the signal nerves use to make muscles contract. Consequently, all of the victim's voluntary muscles will suddenly cramp up for as long as he is exposed to the beam. The full contraction of all of the victim's muscles at full strength is extremely fatiguing, and after a few seconds the victim will lack the energy to move.
When triggered, the electric current flows down one of the parallel beams, passes through the target, and returns along the other. These channels are not focused beams - they keep a near-constant width for their entire path. They need to be wide - several centimeters at least - in order to provide enough ionized charge carriers to conduct electricity. The higher the concentration of ionization, the more rapidly ions recombine with their electrons and the faster the charge carriers disappear. A wide ion channel allows the same number of charge carriers at a lower concentration, and thus allows the channels to be formed with less power lost to re-ionizing the channels. The ion channels glow with the blue-violet light of ionized nitrogen, produce a buzzing sound, and produce the fresh-pungent smell of ozone. On contact with the target, an initial high voltage allows the current to arc across an air gap and several millimeters of intervening material to make electrical contact with the victim. Once current is flowing, the voltage is limited to produce a constant current flow chosen to minimize the chance of serious harm while allowing incapacitation.
In game terms, the stun effect is treated as a carrier that applies basic damage without wounding to reflect the initial arc, with the biological effects as a follow up. Anyone affected by a stun pulse must roll vs. HT-6 or fall down and lose their next action. If they continue to be exposed to the beam, they will be unable to act for the duration of exposure, and one round thereafter. Treat this as a Paralysis and Moderate Pain Affliction that is automatically dispelled one turn after the beam is no longer in contact (the victim gets another resistance roll after a number of seconds equal to the margin of failure. If he made the original resistance roll, he must make another roll on each subsequent turn he is exposed to stun beams). If the victim is hit by the full ROF number of shots, he takes 1 FP. After the victim is no longer exposed to the beam, he is stunned and must roll vs. HT each turn to recover. These effects are not cumulative - if you are hit by one pulse or a dozen during your turn, or a beam from one stun gun or a dozen, you still only lose your next action, take at most 1 FP, and make only one resistance roll to fight off the effects of all the beams.
Stun guns are designed to affect targets with a given SM. For every SM greater than this, the target gets a +3 to resist the effects. The guns may be safely used on targets of smaller SM, but there is no additional penalty to resist. Very small targets with linear dimensions less than the width of the stun gun's aperture will not make electrical contact with both beams, and will be unaffected.
If the stun beams both contact the same piece of metal or other good conductor (or a different conductor with a conductive path between them, such as chain mail), the beam shorts across the conductor instead of the victim and the victim is unaffected. Even a single layer of aluminum foil is enough to block the beam, and just one un-insulated copper wire will suffice to short out the stun effect. Insulators, on the other hand, will not block the beam if they are thin enough - the high-voltage driven current will arc through the insulator to produce a conductive channel. Material strength has little effect on a material's ability to protect against the beam, so DR has no correlation with protective value from stun guns. Instead, each millimeter of air between the end of the ionization beams (for example, where they are blocked by clothes) and the target provide DR 1 for the carrier damage to break through. Any material, clothing, or armor that is woven or porous counts as air, since the arc can pass through the air between the fibers if the fibers have a higher breakdown field than the air. Otherwise, every millimeter of intervening material gives DR 4 (or more, for materials specifically designed for insulation against high voltages, up to DR 10). Usually, the protective value of light clothing or woven armor can be neglected, but if needed the thickness of armor can be found using the rules given on the main beam weapons page under rules for burning through armor (remember to multiply by 10 to get thickness in millimeters). Light clothing can be assumed to be 1 DR, a light jacket 5 DR, and heavy winter clothes 15 DR. Loose clothes with lots of drapery, such as flowing robes or dresses, provide a DR of 10 in hit locations where the cloth is loose and hanging, or more for hoop skirts or other exotica. Remember that the beams are several centimeters wide and the arc will occur where there is the least resistance, so that they can usually find some portion of clothes that are close to the skin even if much of the clothes are held further away by folds, overlapping sections, and drapery.
Although stunners are listed as ROF 5, they actually produce 20 pulses per second, with 4 pulses grouped into one shot for game purposes. If a higher ROF is desired, the player may, as a free action, decide that on his turn he will increase the ROF to 10 or 20 (this is a free action because it just involves swinging the weapon around more rapidly, rather than attempting to keep it focused on one target). This may be beneficial for Spraying Fire (pg. B 409) or Suppression Fire (pg. B409-410). At ROF 10, hits have a +5 to HT to resist; at ROF 20, there is a +8 to resist.
Once a target has been hit, it is often beneficial to keep the beam on him for several turns. This prevents the target from getting back up, allows time to restrain or otherwise deal with the target, and if enough FP is lost it can result in long term incapacitation. If there are no other threats, once the target is down the shooter can claim all applicable non-combat bonuses from GURPS Tactical Shooting (pg. 9), which usually adds +2 to Beam Weapons skill (friendly fire with a stun beam has relatively mild consequences, but the shooter usually has a stake in the outcome and the environment is rarely ideal). Stunners have visible beams, so the Walking The Burst rules from GURPS Tactical Shooting (pg. 16) may come in handy - without the distraction of combat, a +4 to Per to see the beams is justified.
RES guns do not have a maximum range. Instead, for every full multiple of the listed "½D" range, the victim gets a +4 to HT to resist the stun effects. Stunners will not work in vacuum or trace atmospheres, but they actually get longer ranges in lower pressure atmospheres because the electrons can travel farther between bumpting into air atoms which increases the conductivity of the ion channels. Divide the range by the atmospheric pressure relative to sea level on Earth.
Wet skin has less electrical resistance - the victim has a -2 penalty to the resistance roll if his skin is wet. On the other hand, humid air causes the electrons in the ion channels to recombine with their ions more rapidly, increasing the resistance of the air and reducing the range. In wet or humid weather, the ½D range may be reduced to as little as 1/5 its listed value. Stun guns do not work at all underwater.
Stun guns are specifically designed to incapacitate humans without killing them. This involves causing skeletal muscle to contract while not affecting cardiac muscle. By necessity, they were developed by testing on other mammals, and they should be equally effective against other vertebrates. However, their effect on non-vertebrates is unknown. Against alien life forms, there is no knowing what may happen. Some possibilities when used on invertebrates or aliens are
While the default behavior of a stun beam is to cause uncontrolable muscular contractions (so called electro-muscular disruption, referred to here as the stun effect); some models allow the current, voltage, waveform, and pulse duration can be changed to give different effects. Two common choices are:
EMP pulses transmit through armor differently than stun pulses. Anything or anyone with active Scanning Sense (radar), Scanning Sense (imaging radar), or Telecommunication (radio) without the appropriate Protected Sense can have no defense against EMP other than the basic resistance roll. Otherwise, a conductive shell will provide +3 to HT. Armor otherwise provides no protection. The usual protection against EMP is Resistant, which can represent circuit breakers, robust electronics, or electronics located inside of a Faraday cage.
Under the hood: the physics of laser-produced ionized wires.
|7 (∞) burn no wounding
|follow up HT-6 aff (SM -1)
|10 (∞) burn no wounding
|follow up HT-6 aff (SM 0)
|18 (∞) burn no wounding
|follow up HT-6 aff (SM 1)
|10 (∞) burn no wounding
|follow up HT-6 aff (SM 0)
|20 (∞) burn no wounding
|follow up HT-6 aff (SM 2)
Palm Stunner: A small, easily concealable electroshock stunner without a grip or sights. It is a common self defense weapon that can easily fit in a pocket or purse. Skill: Beam Weapons (Pistol). Aperture 2 cm. Beam energy 0.003 kJ. Energy used per shot 0.003 kJ. Extra power cell 0.09 kg, $5.
Stun Pistol: A full-sized pistol for disabling humans and similar sized animals. It is popular with police and prison guards. Skill: Beam Weapons (Pistol). Aperture 3 cm. Beam energy 0.007 kJ. Energy used per shot 0.007 kJ. Extra power cell 0.2 kg, $11.
Restraint Carbine: A compact longarm for longer-range takedowns or for restraining larger subjects. Skill: Beam Weapons (Rifle). Aperture 5 cm. Beam energy 0.02 kJ. Energy used per shot 0.02 kJ. Extra power cell 0.6 kg, $30.
Underbarrel Stunner: A weapon attachment designed to be mounted on the accessory rail of a weapon with Bulk -3 or more to provide less-than-lethal force options. It uses the Bulk, Min ST, and sighting bonuses of the weapon it is attached to. If the Acc of the attached weapon is lower, use that Acc instead. Skill: Beam Weapons (Rifle). Aperture 3 cm. Beam energy 0.007 kJ. Energy used per shot 0.007 kJ. Extra power cell 0.2 kg, $11.
Heavy Stunner: A heavy-duty longarm for driving, capturing, or restraining large animals. Almost all models include prod as well as stun beams. Skill: Beam Weapons (Rifle). Aperture 6 cm. Beam energy 0.03 kJ. Energy used per shot 0.03 kJ. Extra power cell 0.9 kg, $40.
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