Guns 'R' Us - A Rules Addendum for Shadowrun 2nd Edition

Guns 'R' Us - A Rules Addendum for Shadowrun 2nd Edition

by Jens-Arthur Leirbakk (mailme)


These rules were made to offer a greater amount of detail for the skill Firearms B/R. When a decker can build his own deck, and a rigger more or less can build a car to her specifications, why shouldn't a gunsmith be able to modify a weapon or its ammunition above and beyond merely customizing it, and putting a gas vent on it?

These rules are not intended to unbalance the game balance. If a gamemaster finds that they do it's lucky they are optional, don't you think?


Generally speaking, there are two types of modifications one can do with the Firearms B/R - either modifying the weapon itself, or modifying the ammunition the weapon fires. The following modifications are quantified within these rules:

Weapon modifications                  Ammunition modifications
Customization                         APDS
Double Action                         AP (Armor Piercing)
Install external smartlink            Distance round
Install internal smartlink            Explosive
Install Burst Fire mode               EX Explosive
Install Full Auto  mode               Trap round
Calibre modification                  Flechette
Make weapon frame                     Gel
Repair weapon                         Hollowpoint
Remove Burst Fire                     Caseless round
Remove Full Auto                      Magnumloaded round
Barrel length modification            Tracer
Modularization of weapon              Subsonic round
Match-grading of weapon               Normal round
As a direct consequence of the rules presented here, Firearms B/R is expanded with a new concentration, namely Firearms B/R : Ammo. Under Ammo, there is a new specialization as well, in every Firearms-type weapon, i.e. Light Pistol, Heavy Pistol, SMG, and so on. When ammunition is custom-loaded, this concentration and its relevant specialization is used.


For every modification discussed, some information is given on the format Equipment, TN, Time and Cost.

Equipment lists the level of equipment needed to do that modification. The equipment can be either a Firearms B/R kit, Firearms B/R shop, or a Firearms B/R facility. If one have a better level of equipment available than that needed, one gets a bonusdie for every level one has better equipment. Example: If the modification needs a kit, and one has a facility, one get 2 bonus dice. If the modification needs a shop, and one has a facility, one gets only 1 bonus die.

The usual rules for TN and Time are in effect, i.e., that Time is divided on the number of successes. 0 successes indicates that the modification was unsuccessful - Cost is wasted, but nothing more. If the item modified was a weapon, the weapon isn't damaged. If the item modified was ammunition, all the 10 rounds was destroyed through some mishap or other not harmful to the character. In the case of ammunition, the GameMaster may also arbitrarily decide that one or more of the rounds loaded is either a dud or a misfire, possibly damaging the weapon.

A Critical Failure indicates that not only was the items the character was working on destroyed, but 10% of the equipment the character used is damaged (and the character must fork out the equivalent amount of nuyen, including Street Index, to repair it). A nice GameMaster (yeah, right) can decide to roll 10+1d6 boxes of damage to determine the extent of the damage to a weapon difficult or nearly impossible to get hold of.


A Firearms B/R kit is 1000 nuyen, with a Street Index of 2 and an Availability rating of 5/48 hours. A Firearms B/R shop is 10 000 nuyen, with a Street Index of 3 and an Availability rating of 8/72 hours, and a facility is 200 000 nuyen with a Street Index of 4 and an Availability of 14/7 days. In addition to the price of the equipment itself, is the Cost of the modification, representing the gunpowder, circuits and so on the modification entails. The GameMaster may also demand a Firearms Theory skill in order to allow the weapon smith to design his own weapons, or make weapon frames.


Customization is usually the last modification a weapon undergoes before it is taken into use. Customizing is usually done on a new weapon, although there isn't anything preventing the customization of an older weapon. Customization is possible for any weapon, though this particular customization procedure is meant for Firearms. The TN and Time is based on how often the gunsmith is allowed to check his measurements, and get feedback from the customer.

If the person having a weapon customised for her is there the whole time the gunsmith is working, the TN and time is +0/+0. If the gunsmith can control his measurements one or two times (that is, two or three measuring sessions in toto), the TN and time is modified +1/+8 hours. If the gunsmith can take the measurements he needs only once, the TN and time is modified +2/+24 hours.

Customization gives one bonus die when the weapon is used by the person it is customized for. Anyone else must take a one die penalty when using the weapon. If the weapon must be used by the person it is customized for in an unaccustomed manner, for instance in the person's "off" hand, then even the person the weapon is customized for will get the penalty die.

In its ultimate form, customization can be extended to only apply to one configuration of the weapon, i.e. if it is customized with a Sound Suppressor system, and not a Gas Vent, then if the Sound Suppressor is replaced with the Gas Vent, the bonus die for customization "disappears", though all the negative effects are still there.

Removing customization of a weapon is a TN 4/12 hour task costing 100 nuyen, a procedure in which the weapon smith replaces the fancy custom grip, trigger and barrel weights with the down-to-earth, standard ones.

Equipment: Shop. TN: 4. Time: 36 hours. Cost: Less of base price or 650 nuyen.

Double Action
The Double Action modification can only be installed on revolvers. Since there's only one in the base system, namely the Ruger Super Warhawk, this is not usually a problem. The Double Action modification upgrades the SS firing mode to a SA firing mode for revolvers only.

A revolver with this modification has an extra +1 recoil modifier, so that shot number two has a +2 recoil modifier. This is exempt all other modifications on recoil because of other factors, for instance magnumloaded ammunition.

Equipment: Shop. TN: 4. Time: 24 hours. Cost: Less of base price or 400 nuyen.

Installing external/internal smartlink
To install a smartlink in a weapon is a relatively trivial operation, and gunsmiths do it all the time. However, it is somewhat more difficult to install a Smartlink level 2 than the regular smartlink, and this is translated to a +2 in the TN for a Smartlink level 2 install.

An internal smartlink increases the weight of the weapon by .5 kg, and an external smartlink increases the weight of the weapon by 1 kg. (I find this somewhat absurd, and suggests that the relevant weights are halved, i.e. .25 kg for an internal smartlink and .5 kg for an external smartlink.)

The external smartlink is listed first, with the internal afterwards. The external smartlink will use either the top- or under-barrel mount.

Equipment: Facility. TN: 3/4. Time: 24 hours / 72 hours. Cost: Either 600 nuyen (external smartlink) or base price of the weapon (internal). The price of a Smartlink level 2 is given in FoF.

Install Burst Fire
This modification entails tinkering with the trigger mechanism to enable the weapon to fire in burst fire mode. The following conditions must be met: The weapon cannot be SS in its "vanilla" version, the weapon cannot be pump-action, and it must either have FA or SA (or both) already. The Gamemaster should use his discretion in odd instances.

This modification allows the weapon to fire a burst as a Complex Action, like the Savalette Guardian. If the gunsmith desires to install a full BF mode, this is a +5 to the TN, in addition to the weapon getting a +2 recoil modifier to its BF if it is a pistol (heavy, machine, light, or hold-out).

Equipment: Facility. TN: 5. Time: 36 hours. Cost: Base price or 850 nuyen, whichever is more.

Install Full Auto
This modification is similar to the BF modification, in that the weapon smith modifies the weapon's trigger mechanism to enable FA fire. The following conditions must be met: The "vanilla" weapon must have Burst Fire, and the weapon cannot be pump-action.

The Gamemaster may allow this modification to be done on pistols if the Gamemaster feels like it, but the TN should be increased with at least +3, and the weapon should use Heavy Weapons recoil.

Equipment: Facility. TN: 6. Time: 48 hours. Cost: Either two times bace price or 1850 nuyen, whichever is more.

Calibre modification
As the name of this modification implies, the gunsmith alters the calibre of the weapon. The rules given for this modification is also used if a gunsmith wishes to alter a weapon firing cased ammo to firing caseless ammo, and vice versa.

Downscaling the calibre of the weapon is usually quite simple. Exactly what is considering a lesser calibre is for the GM to decide, but the progression (from least to most) is: Hold-Out Pistol (often special ammo), Light/Machine Pistol, SMG, Assault Rifle, Sporting Rifle, Heavy Pistol, Sniper Rifle, Shotgun, Custom 121 ammo.

If a weapon is converted to using caseless ammunition, the rules given in Fields of Fire for caseless ammunition is used, i.e. that the ammunition costs 150% of normal price, the weapon can take 20% (round down) more rounds in its clip or magazine, and the ammunition is 20% (round up) lighter.

If a weapon is modified from using caseless ammunition, the magazine or clip can take [rounds/1.2] (round down) rounds, and that the weight of the ammunition is normal.

Increasing the calibre of the weapon is only possible one step, and Custom 121 isn't an option - no other weapon than a Barrett should be able to fire Custom 121 ammunition. The same is to a certain extent true for shotgun ammunition - that another weapon than a shotgun can fire shotgun ammunition is slightly absurd - but the GM may allow it.

The weapon uses its normal ranges in any instance, but the damage is modified by the new calibre the weapon fires, either up or down (often 4L-6L-7M-8M-8S-9M-12S-10S-14D, but ultimately GM's discretion). If the calibre modification was to a larger calibre, the weapon uses Heavy Weapons recoil. If a mishap or Catastrophic Failure happens, there is a much greater risk for the weapon actually blowing up if the calibre was increased, since the weapon is exposed to much greater stress from the larger round it is firing.

The ammunition capacity of the weapon is also modified, unless special circumstances apply (GM's decision). A suggestion is 30% either increase or decrease, depending on whether the calibre was reduced or increased.

Because this modification is so flexible and variable, the GM should pay good attention when this modification is employed on a weapon.

Caseless (to or from)
Equipment: Shop. TN: 5. Time: 24 hours. Cost: More of 500 nuyen or base price.
Decrease Calibre
Equipment: Shop. TN: 4. Time: 24 hours. Cost: Less of 350 nuyen or base price.
Increase calibre
Equipment: Facility. TN: 8. Time: 96 hours. Cost: More of 1000 nuyen or twice base price.

Make Weapon Frame
A gunsmith usually buys a weapon to modify to her heart's content. However, if the gunsmith insists, it is possible to make one's own weapon frame to modify.

The frame made cannot fire - a trigger mechanism must be installed. This is usually a TN 4 test, +1 for either SS, SA or FA, +2 for SA/BF, +3 for BF/FA, and +4 for SA/BF/FA. The trigger mechanism must also be the typical for the weapon concerned, i.e. SA for Light Pistol, SA/BF for an SMG, and FA for an LMG. The damage and ammo capacity is as per the "standard" weapon of that type, i.e. dependant on the GM's discretion. The Ares firearms are usually an useful baseline.

Equipment: Facility. TN: 6 (frame) / 5+ (trigger). Time: 7 days. Cost: (total) 200 times the Power of the weapon's damage.

Barrel length modification
Modifying the length of the barrel of a weapon has one of two effects, depending on whether one increase or decrease the length of the barrel. If one shorten the barrel, the weapon will be easier to hide, but will also suffer from a shorter range. If one lengthen the barrel, the weapon will be more unwieldy, but the range of the weapon will be increased.

Exactly what weapons eligible for barrel length modification are up to the GM, but a suggestion is as follows: shotguns and rifles can get shortened barrels, while pistols and SMGs can have their barrels lengthened.

A weapon with a longer barrel cannot be used with Quick Draw, gets one step range increase (for instance from Light Pistol to Heavy Pistol), and Concealability is reduced by at least 1 (GM's decision, but a 1 or 2 point decrease in Concealability is fair).

If a weapon is shortened, it gets one step shorter ranges (for instance, from Light Pistol to Heavy Pistol), and Concealability is increased by 1.

Shotguns are somewhat special, since their stock can also be removed. If the stock is removed, Concealability will be increased by 1, the shotgun cannot use shock pads or any other similar stock modification, and the shotgun gets an extra +2 recoil modification. This modification can of course not be used on a Remington Roomsweeper. Weapons with a folding stock will use their greater Concealability if the stock is removed.

Equipment: Kit. TN: 4. Time: one hour. Cost: Nothing (unless you break the blade of the hacksaw).
Equipment: Shop. TN: 4. Time: 6 hours. Cost: More of 10% base price or 300 nuyen.

This modification entails keeping the weapon in an absolute peak condition, a far better condition than is needed to keep the weapon in a good working order. Using a match-graded weapon awards one bonus die.

Match-grading lasts for a number of shots equal to a "normal" magazine for the weapon or 12 shots, whichever is more. After this, the weapon loses its match-grading, but can be tuned up to match-grade quality again, for a maximum of five times total. Customization is cumulative with match-grading, and even though the match-grade will be worn out, the customization will not be worn out.

Match-grading is very sensitive, and any situation where the Gamemaster feels there's a good chance for the weapon to get a good thump there's a chance the match-grading is ruined. The Gamemaster (or the player, for that matter) rolls 5 dice against a TN the GM determines - for instance, 4 if the weapon is in a special suitcase or other padded carrying device, 8 if the weapon is dropped to the floor, and so on. One success is enough to save the match grade.

Equipment: Facility. TN: 3 (+1 per tuneup). Time: 48 hours. Cost: 20% of base price.

Modularization of weapon
This option enables the weapon to be both assembled and disassembled with one's bare hands, so to speak. This is the option used for the "classic" sniper rifle, not to mention the gun used by Scaramanga in "The Man With The Golden Gun". If the weapon is match-graded and modularized, it is particularly sensitive to any stress, and gets +4 on the test to resist losing its match-grading.

The Ranger Arms SM-3 rifle given in SRII has this option, and the rules given for that weapon also applies for any weapon with this option (i.e., a 2D6 check with a TN of the number of turns it was under stress, or a +2 TN with the weapon due to unaligned parts). To re-align the parts one needs a kit, and rolls against a TN 4 / 4 hours test.

Equipment: Facility. TN: 5. Time: 72 hours. Cost: 25% of base price.

Repairing a weapon
Weapons can also be damaged, perhaps more frequently so after the introduction of magnum-loaded ammunition. A weapon in the Shadowrun system has a damage monitor of 10 boxes, with the same severities on damage as usual. The amount of equipment and money needed to repair a weapon depends on how badly the weapon is damaged.

If the weapon has more than Deadly damage, the GM rolls 1d6, rerolling the 6-es as usual, and adds the amount of boxes the weapon has taken in damage. If the GM's total is more than 18, the weapon cannot be repaired, as it is too severely damaged. Also, one cannot repair the weapon in "stages" to reduce the overall cost. The time given will restore the weapon to normal condition, no matter the severity of the damage to the weapon.

Light damage
Equipment: Kit. TN: 3. Time: 12 hours. Cost: 5% of base cost per box repaired.

Medium damage
Equipment: Kit. TN: 4. Time: 24 hours. Cost: 6% of base cost per box repaired.

Serious damage
Equipment: Shop. TN: 5. Time: 36 hours. Cost: 7% of base cost per box repaired.

Deadly damage (10+ boxes)
Equipment: Facility. TN: 8. Time: 72 hours. Cost: 8% of base cost per box repaired.

Remove Burst Fire
The gunsmith may decide to remove Burst Fire from a weapon, for some reason. If the weapon's only mode of fire is BF, the mode is reduced from BF to SS. Otherwise, merely remove BF from the modes the weapon can fire.

Equipment: Shop. TN: 5. Time: 12 hours. Cost: Less of half base price or 400 nuyen.

Remove Full Auto.
Similar to BF, this modification cannot be made on gatling-style weapons.

Equipment: Shop. TN: 6. Time: 24 hours. Cost: Less of base price or 1200 nuyen.


Modifications on ammunition can be made on two parts - the projectile and the powder charge. The type of modification is given in the header of the modification, i.e., usually either projectile and powder charge. Together they make up one round of ammunition. The separate parts of a round can have only one modification each. The tests and cost are for 10 rounds, unless something else is denoted in the description of the round.

The Gamemaster may demand that the gunsmith must have Firearms Theory, and even roll checks versus the skill to make the more exotic rounds, such as APDS and EX Explosive. One can also use the projectiles from rounds one already have, and only modify the powder charge. The reverse is not true - a round must be reloaded after it is opened.

These rules do not cover Custom 121 ammunition, as they are. A suggestion to making custom 121 ammunition is to multiply all prices with 10, and use the APDS and magnum-load options to simulate the way the custom 121 ammunition works.

APDS ammunition (projectile)
APDS ammunition was introduced in the Street Samurai's Catalog, and is perhaps the most effective ammunition in the Shadowrun system. APDS is an acronym for Armor Piercing Discarding Sabot, which is technobabble for "that which you shoot a guy in heavy armor with".

APDS ammunition isn't easy to gethold of, and therefore gunsmiths may want to make their own. Which isn't easy.

Equipment: Facility. TN: 10. Time: 12 hours. Cost: 200 nuyen.

AP (Armor Piercing) (projectile)
An AP round is just a round made for easier to penetrate armor. This translates into a -2 ballistic armor penalty, or halves the armor value (rounds down) of the opponent, whichever is less. This round is also considered AP versus Hardening.

Equipment: Shop. TN: 8. Time: 8 hours. Cost: 150 nuyen.

Distance round (powder charge)
The distance round is a more evenly packed powder charge, with a better and more complete burn. This improves the ballistics of the round in question. This round gives a -1 TN bonus on ranges starting from Medium range.

Equipment: Shop. TN: 6. Time: 4 hours. Cost: 100 nuyen.

Explosive (projectile)
This is the "standard" explosive round as given in SRII.

Equipment: Shop. TN: 5. Time: 7 hours. Cost: 40 nuyen.

EX Explosive (projectile)
This is the EX-round as given in the Fields of Fire sourcebook.

Equipment: Shop. TN: 6. Tid: 10 hours. Cost: 150 nuyen.

Trap round (projectile & powder charge)
This round is meant to destroy the chamber of the weapon when it is fired. Exactly how damaging this is depends on how this is done.

If the rest of the magazine is loaded with volatile ammunition, for instance Explosive ammunition, the GM may roll a test to see if the rest of the ammunition detonates when the trap round detonates, which can lead to rather nasty consequences. The test is similar to the one for elemental effects in The Grimoire.

A trap round does (TN)d6 boxes of damage to the weapon it was attempted fired in, but can be discovered by an inspection of the trap round by a person used to weapons (Firearms B/R 3 or Firearms 5 to discover any trap rounds in a batch of 10 rounds).

If the test to create the trap round was unsuccessful (0 successes), the trap round is a dud (Firearms B/R 6+TN to discover this). If the test was a catastrophic failure, the round actually blew up in the face of the gunsmith. This is the equivalent of a TN(M) attack, without the benefit of any armor.

Equipment: Facility. TN: variable. Time: (TN/2) hours. Cost: 5*TN nuyen (one round).

Flechette (projectile)
This is the standard Flechette-round as given in SRII. This option is also used if one is loading a standard shot-round for a shotgun.

Equipment: Shop. TN: 5. Time: 4 hours. Cost: 90 nuyen.

Gel (projectile)
This is the standard Gel round as given in SRII.

Equipment: Shop. TN: 5. Time: 5 hours. Cost: 30 nuyen.

Hollowpoint (projectile)
Hollowpoint ammunition can be made with no more than a Kit if one uses "regular" ammunition, which one simply drills a pit in the point of the ammunition. If the gunsmith makes the projectile from the bottom up, the equipment needed is equivalent to a Shop. Hollowpoint ammunition increases the Damage Level with one to a maximum of Deadly, but increases any Ballistic armor the target wears with +2.

Equipment: Kit / Shop. TN: 5. Time: 1 hour / 8 hours. Cost: Nothing (one regular round) / 100 nuyen.

Caseless (projectile & powder charge)
Caseless ammunition is merely somewhat more difficult to make than the normal (cased) version of whatever projectile in question. Magnum loading of caseless ammunition is even more difficult - +1 TN on any modification, with an extra +1 for the magnum load powder charge modification.

Equipment: Shop. TN: +1/+2. Time: +2 hours. Cost: +20%

Magnum load (powder charge)
A magnum loaded round is a little more than a round with extra gunpowder in the poor cartridge. But not particularly more.

There's a greater chance for weapon jam or damage with a magnum loaded round - the Critical Failure chance increases from the Rule of Ones to the Rule of Ones & Twos, i.e., that if an attack roll generates only ones and/or twos, a Critical Failure has occured.

Magnum loading gives an extra +1 recoil per magnum round fired, and gives +1 Power on Short range and Medium range.

Equipment: Shop. TN: 6. Time: 6 hours. Cost: 90 nuyen.

Tracer (projectile)
A tracer round, or "lit" round isn't particularly difficult to make, and can easily be made out of regular ammunition. The rules for Tracer rounds can be found in the Fields of Fire Shadowrun sourcebook. A Tracer round can also be made from the bottom up. See hollowpoint for a similar round.

Equipment: Kit/Shop. TN: 5. Time: 1 hour / 8 hours. Cost: 20 nuyen (phosphorus and stuff) / 100 nuyen.

Subsonic round (powder charge)
A subsonic round propels the projectile at a speed slower than sound. The efficiency of sound dampers (silencers and sound suppressors) is increased if this powder charge is used.

The Power of the projectile is reduced by one. Subsonic rounds give an extra +2 TN to hear the firing of the weapon. This modification shouldn't be combined with explosive rounds or any other rounds that make much noise when they hit.

Equipment: Shop. TN: 4. Time: 5 hours. Cost: 30 nuyen.

Regular round (projectile & powder charge)
To make a regular round to a weapon, this option is the one to use. If a special powder charge or special projectile has been chosen, and one needs a "regular" other half to complete the round, this option is also the one to use.

Equipment: Shop. TN: 3 / 3. Time: 4 hours / 4 hours. Cost: Projectile: 20 nuyen, powder charge: 20 nuyen.


Shotgun round - 14D(f) (flechette effect already figured in). The common Assault Cannon has a Choke of 4. Availability 5 / 3 days, 400 nuyen, Street Index 2.

Impact / Stun round - 12M Stun, otherwise normal round. 5 / 3 days, 400 nuyen, Street Index 2.

Penetrator round - 16S AP, otherwise normal round. 14 / 14 days, 1000 nuyen, Street Index 4.

Taken from the pages of Jens-Arthur Leirbakk