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Weapons & ballistics

1.13 is famous for its huge gun catalog, but the deeper change is what happens around the trigger: a real ammunition system with dozens of ammo types, guns that heat up, foul up, wear out and jam, and a set of stances and rests that change how well you shoot. This page covers those mechanics. For how aiming and chance-to-hit work, see NCTH; for scopes, grips and lasers, see attachments; for where to put all those magazines, see the inventory system.

The ammo system

Calibers and magazines

Every gun is chambered for a caliber (9x19mm, 5.56x45mm, 7.62x51mm, 12 gauge…) and only accepts ammunition of that caliber. Ammunition comes as items defined in Data-1.13\TableData\Items\Magazines.xml: each entry couples a caliber, a magazine size, an ammo type (see below) and a container type. There are four container types in the game data:

Container What it is
Magazine A normal mag/clip/belt — load it straight into a matching gun.
Loose rounds Small bundles (e.g. "7.62x51mm Bullets, 5") for guns that load single rounds; reloading loose rounds costs AP per round (AP_RELOAD_LOOSE in APBPConstants.ini).
Box A cardboard box of loose ammo. Can't be loaded directly.
Crate A big ammo crate. Can't be loaded directly.

Boxes and crates are bulk storage: outside combat, drop a box or crate onto a gun of matching caliber and ammo type and the game converts its contents into ready magazines sized for that gun. The reverse works too — drop leftover magazines onto a matching box or crate to pour the rounds back in. This is the practical way to manage the mountains of ammo you buy from Bobby Ray's.

With DYNAMIC_AMMO_WEIGHT = TRUE (the default, in Ja2_Options.INI), magazines weigh less as they empty, so half-used mags aren't dead weight.

The colored number shown on a loaded gun tells you the ammo type at a glance — each type in AmmoTypes.xml defines its own display color (grey for Ball, red for AP, and so on).

Ammo types

The ammo type is where ballistics happen. Each type in Data-1.13\TableData\Items\AmmoTypes.xml modifies how the bullet interacts with armor and flesh. The two numbers that matter most:

  • Armor modifier — multiplies the protection value of body armor the bullet hits. Lower is better for you: AP ammo at ×0.75 makes the target's vest a quarter weaker; Glaser at ×3 makes it three times stronger.
  • Damage after armor — multiplies whatever damage makes it through. Hollow points at ×1.7 tear up unarmored targets; the flip side is that against armor their damage can be reduced to zero.

The everyday types, with the current data values:

Type Armor protection Damage after armor Heat/shot Dirt/shot Notes
Ball ×1.0 ×1.0 — — The baseline; what the AI is issued.
AP / FMJ ×0.75 ×1.0 +13% +20% Extra chance to punch through the target and keep flying.
SAP ×0.5 ×1.0 +30% +20% Semi-armor-piercing: even better vs armor.
HP ×1.5 ×1.7 −17% +10% Devastating vs soft targets; vs armor, damage can drop to 0.
HP Solid ×0.9 ×1.5 −3% +20% Solid-copper hollow point: HP effect without the armor helplessness.
Match ×1.0 ×1.0 +8% +15% Match magazines add +10% gun accuracy (PercentAccuracyModifier on the item). Match FMJ also gets the ×0.75 armor modifier.
Tracer ×1.0 (Ball) / ×0.75 (FMJ) ×1.0 +25–35% +40–50% See tracers and autofire. Tracers defeat flash suppressors and give your position away.
Cold (subsonic) as base type ×0.95 (Ball) to ×0.75 (AP/SAP) lower lower Cold magazines carry a 40% noise reduction that stacks with suppressors — the quiet choice for stealth work.
Glaser ×3.0 ×3.0 −20% +8% Frangible: brutal against bare flesh, nearly useless against vests.
Buckshot ×1.0 ×1.0 — — 9 pellets per shell with a spread pattern.
Flechette ×0.8 ×1.0 +3% −25% 20 darts per shell, high chance to over-penetrate.
Duplex ×1.0 ×1.0 +15% +30% Two bullets per cartridge with a slight spread.

Special-purpose types you will run into:

Type Effect
Rubber Armor ×5, health damage ×0.3, breath damage ×1.3 — less-lethal rounds for knocking people out, e.g. to take prisoners.
Lock Buster +100 damage to locks: shotgun breaching rounds.
AET ×0.75 armor and ×1.7 after armor — best of AP and HP, runs hot (+35% heat).
Depleted Uranium ×0.5 armor, big over-penetration chance, and corrodes armor four times faster.
Darts / Neurotoxin darts Ignore torso and leg armor; accurate hits can put the target to sleep (dart guns).
Pepper spray No damage; blinds the target on head hits.

A few exotic types (Cryo, Flame, Fire retardant, anti-materiel) exist in the data for sci-fi mode and mods — their fields (freeze, fire trails, structure destruction) are documented in the AmmoTypes.xml header comments. See XML files if you want to read or tune the raw data.

Tracer magazines

Tracer mags aren't all tracers: NUM_BULLETS_PER_TRACER = 5 in Ja2_Options.INI means every 5th round glows. Tracers do two things: they draw a visible line every observer can react to (bad for stealth, and flash suppressors don't hide them), and with REALISTIC_TRACERS = 2 (the default) each tracer fired in a burst gives the shooter a chance-to-hit bump for the rest of the volley (CTH_BUMP_PER_TRACER = 20, effective beyond MIN_RANGE_FOR_TRACER = 10 tiles). Long machine-gun bursts walk onto the target noticeably better with mixed tracer belts.

Reliability, condition and jamming

Every shot fired can jam the gun. The chance is computed from three things you control and one you don't:

  • Condition — the gun's status percentage. Worn guns jam more.
  • Reliability — a hidden per-item stat (bReliability in Items.xml, roughly −6 to +5 in current data, visible in the item description box). The gun, the loaded magazine and every attachment each contribute — cheap ammo makes good guns jam too.
  • Dirt and heat — see the next two sections.
  • Weather — rain and storms reduce effective reliability (WEAPON_RELIABILITY_REDUCTION_THUNDERSTORM = 1, _SANDSTORM = 4, _SNOW = 2, _RAIN = 0 in Ja2_Options.INI; see environment).

The per-shot jam chance is capped based on reliability — in current code the cap runs from just a few percent for very reliable guns to over 50% for junk. Enemies suffer jams too (ENEMY_JAMS = TRUE in [Tactical Gameplay Settings]).

A jam wastes the round and marks the gun JAMMED. On low-condition guns the jam can also damage the gun — including permanent damage (see below); the condition threshold where that risk starts is per weapon class (JAM_DAMAGE_THRESHOLD_* in Item_Settings.ini, e.g. 65 for assault rifles, 30 for shotguns).

Unjamming: just pull the trigger again — the merc spends a couple of AP (AP_UNJAM = 2 on the 100-AP scale) and makes a Mechanical/Dexterity check (easier with reliable guns). Revolvers and a few other designs are flagged EasyUnjam in Weapons.xml and always clear instantly. A merc on Repair duty also clears jams as part of repairing (REPAIR_POINT_COST_TO_FIX_WEAPON_JAM = 2).

Weapon overheating

Overheating is a Flugente feature from 2011 that is off by default: enable it with OVERHEATING = TRUE in [Tactical Weapon Overheating Settings], or flip the Weapon Overheating toggle on the 1.13 Features screen when starting a campaign.

Heat, jams and damage

Every shot adds temperature to the gun — usOverheatingSingleShotTemperature in Weapons.xml, scaled per weapon class in Item_Settings.ini and by the ammo type (tracers +25–35%, hollow points −17%). Autofire is what really builds heat: a 40-round burst from an M60 adds 40 × 140 temperature.

Each gun has two thresholds in Weapons.xml:

  • Jam threshold (usOverheatingJamThreshold) — above it, the jam chance climbs steeply with every extra percent of temperature.
  • Damage threshold (usOverheatingDamageThreshold) — above it, the gun wears out much faster (the extra wear grows with the square of how far over you are) and the gun's inherent accuracy drops (roughly −10% per full multiple over the threshold).

Some current data points:

Gun Heat/shot Jam threshold Damage threshold
Glock 17 45 20,000 13,500
Colt M16A1 125 40,000 14,500
AK-47 117 40,000 11,200
FN Minimi 125 40,000 25,000
M60E3 140 40,000 21,000

A thermometer bar appears next to the weapon's picture, and the description box shows the temperature. OVERHEATING_DISPLAY_JAMPERCENTAGE = TRUE makes the displayed percentage mean temperature vs jam threshold (set it to FALSE to track the damage threshold instead).

Cooling down and spare barrels

Guns cool a little every turn (about every 5 seconds in real time) — including guns lying on the ground or in sector inventory. Each gun has its own cooling rate (usOverheatingCooldownFactor in Items.xml), and attachments slow it down: in the current data suppressors cost −20%, a barrel extender −15%, a flash suppressor −3% (overheatCooldownModificator on the attachment items).

Machine gunners get a hardware solution: the game data contains five caliber-specific replaceable barrels (5.56x45mm, 7.62x51mm, 7.62x54R, 5.45x39mm, 7.62x39mm). Merge a fresh barrel onto a compatible belt-fed MG (50 AP) and the gun and the spare barrel swap temperatures — the hot barrel goes into your pack to cool off, and it cools 15% faster when it isn't being carried (OVERHEATING_COOLDOWN_MODIFICATOR_LONELYBARREL).

INI reference

Current Ja2_Options.INI, [Tactical Weapon Overheating Settings]:

Setting Default What it does
OVERHEATING FALSE Master switch for the feature.
OVERHEATING_DISPLAY_JAMPERCENTAGE TRUE Displayed percentage = temperature/jam threshold (TRUE) or temperature/damage threshold (FALSE).
OVERHEATING_DISPLAY_THERMOMETER_RED_OFFSET 100 Starting amount of red in the thermometer bar (0–255).
OVERHEATING_COOLDOWN_MODIFICATOR_LONELYBARREL 1.15 Barrels not in anyone's inventory cool this much better.

Per-class fine-tuning (OVERHEATING_JAM_THRESHOLD_*_MODIFIER, OVERHEATING_TEMPERATURE_*_MODIFIER, OVERHEATING_COOLDOWN_*_MODIFIER for pistols, SMGs, rifles, LMGs…) lives in Item_Settings.ini.

Old documentation describes settings that no longer exist

The original feature announcement (and wiki pages copied from it) lists INI keys like OVERHEATING_MAX_TEMPERATURE, OVERHEATING_DISPLAY_THERMOMETER and per-attachment cooldown modifiers (..._SILENCER, ..._BARRELEXTENDER, ..._FLASHSUPPRESSOR). None of these are in the current Ja2_Options.INI: the maximum temperature is now a fixed constant in the source (60,000), and the attachment modifiers moved into per-item tags in Items.xml.

Dirt and fouling

The advanced repair/dirt system (Flugente, 2012) is on by default in current releases (ADVANCED_REPAIR = TRUE). It has two halves.

Guns get dirty

Firing fouls the gun. In the current code this shows up as accelerated condition loss: each shot's chance to knock a point off the gun's status is multiplied by a dirt factor built from:

  • the gun's own DirtIncreaseFactor in Items.xml — an M16A1 (60) fouls six times faster than a SCAR (10); an AK-47 sits at 18,
  • the ammo type (dirtModificator in AmmoTypes.xml — tracers +40–50%, AP +20%),
  • attachments (each can add its own factor),
  • the global DIRT_GLOBAL_MODIFIER = 1.25,
  • where you are: every sector has a <usNaturalDirt> value in TableData\Map\SectorNames.xml — around 100 in towns, up to 1000 in the desert. Fighting indoors halves it,
  • weather: thundershowers ×1.2, snow ×1.1, sandstorm ×2.0.

So the same M16 that soldiers on for a whole town battle can start rattling apart after a couple of magazines in a desert sandstorm. Dirty, worn guns then jam more (condition is part of the jam formula above).

The 2012 version worked differently

The original announcement described a separate dirt meter with its own INI keys (DIRT_SYSTEM, FULL_REPAIR_CLEANS_GUN, SECTOR_DIRT_DIVIDER) and passive dirt accumulation over time. Those keys are gone from the current Ja2_Options.INI; today dirt only accrues when firing, and it is folded into the gun's condition.

Cleaning kits

The cleaning kit item removes fouling. Two ways to use it:

  • In the field: press Ctrl+. to open the Action menu and choose the cleaning option (see hotkeys). Out of combat your guns are cleaned on the spot; during combat it costs serious time (AP_CLEANINGKIT = 80 on the 100-AP scale in APBPConstants.ini).
  • On assignment: a merc on Repair duty who has a cleaning kit also cleans every dirty gun in the sector (speed governed by CLEANING_RATE_DIVISOR = 500; see facilities & assignments). Cleaning even trains Mechanical and Dexterity a little.

Kits wear out slowly with use. Cleaning restores gun condition up to the gun's repair threshold — which brings us to the second half of the system.

Permanent damage and gunsmiths

With ADVANCED_REPAIR = TRUE, weapons and armor carry a hidden repair threshold. Damage — hard use, jams on worn guns, battle damage — can permanently lower it, and your mercs can only repair or clean an item up to that threshold, not back to 100%.

Two ways to restore the threshold itself:

  • Arulco's repair merchants (Perko, Fredo, Arnie & co.) fix items all the way — the intended money sink; see the economy page.
  • Technicians, if you set MERCS_CAN_DO_ADVANCED_REPAIRS = TRUE in Skills_Settings.INI (default FALSE; TECH_LEVEL_NEEDED_FOR_ADVANCED_REPAIR sets whether one trait level is enough — see traits).

INI reference

Current Ja2_Options.INI, [Strategic Gameplay Settings]:

Setting Default What it does
ADVANCED_REPAIR TRUE Guns/armor can take permanent damage only gunsmiths (or enabled Technicians) can fix.
ONLY_REPAIR_GUNS_AND_ARMOUR FALSE Restrict merc repair to guns and armor only.
DIRT_GLOBAL_MODIFIER 1.25 Scales dirt generation for all guns (0.1–10.0).
ADDITIONAL_REPAIR_MODE TRUE Priority-based repair order (equipped weapons first, most-damaged first) instead of merc-by-merc.

Recoil, tracers and autofire control

Burst and autofire behavior is an NCTH topic — each gun has a recoil pattern and your shooter fights it with counter-force based on strength and skill — so this page just lists the levers that make sprays controllable:

  • Foregrips, grippods and bipods reduce autofire climb; see attachments.
  • Tracer ammo bumps CTH mid-burst (see above).
  • Weapon resting: with WEAPON_RESTING = TRUE (default), a merc standing or crouching behind a crate, rock, window sill or table rests the weapon on it and receives part of the prone-position bonuses (WEAPON_RESTING_PRONE_BONI_PERCENTAGE = 50). Fight from cover — it's not just protection, it's accuracy.
  • Raise your weapon (L or middle mouse button — see hotkeys): several bonuses only apply with a readied weapon.

Alternative weapon holding

ALLOW_ALTERNATIVE_WEAPON_HOLDING (in [Tactical Gameplay Settings]) lets mercs fire rifles from the hip and pistols one-handed (the standard pistol grip is two-handed). The alternative hold is fast — readying costs only 25% of the normal ready AP and shots cost 10% fewer AP — but inaccurate: a base −30 CTH penalty, reduced aim levels, and no scope use. It currently works in standing position only.

The setting's value picks the behavior (the INI comment block documents all four):

Value Behavior
0 Feature off.
1 Un-aimed snap shots with a lowered weapon automatically fire from the hip / one-handed.
2 The first few aim clicks (shown as yellow dots under NCTH) fire from the alternative hold; aiming past them raises the weapon properly.
3 Default — "scope mode": the alternative hold appears as an extra mode (an eye symbol) when you cycle sights with . or Q. Requires USE_SCOPE_MODES = TRUE (default).

Fine-tuning keys, same section, current defaults: RAISE_TO_ALTWEAPHOLD_READY_APS_PERC = 25, RAISE_FROM_ALTWEAPHOLD_READY_APS_PERCENTAGE = 75, FASTER_SHOT_FROM_ALTWEAPHOLD_PERC = 10, CTH_PENALTY_FROM_ALTWEAPHOLD = 30, AIMING_PENALY_FROM_ALTWEAPHOLD = 30 (sic), AIMING_LEVELS_REDUCTION_ON_ALTWEAPHOLD = 50.

Modders can flag two-handed guns as <HeavyGun> in Weapons.xml so they can only be fired from the hip while standing; the stock data currently doesn't use the flag.

Sources