Caliber ID Registry

Intermediate40-60 minutesWindowsNotepad++Unity Editor

The caliber ID is the numeric key that links a gun to its compatible magazines in Unturned™. Every gun declares the caliber it accepts; every magazine declares the caliber it supplies. When the two values match, the magazine seats in the gun and can be fired. When they do not, the magazine is silently rejected with no error message, no log entry, and no visual feedback - the attachment slot simply refuses the item. Understanding the caliber ID system is therefore the single most important prerequisite for authoring a working gun mod.

This article is the 57 Studios™ canonical registry of known caliber IDs, their mappings to in-game round designations, and the conventions for assigning new IDs to custom mod content. It complements the Caliber Asset article, which covers the GUID-based caliber asset system and the ballistic parameter set that caliber assets can carry. Where the Caliber Asset article describes the what and how of caliber configuration, this article describes the registry - the known set of numeric IDs, their assignments, and the rules for adding new ones.

Who this article is for

This article is written for Unturned™ mod authors who have read the Gun Mod Tutorial and understand the basic structure of gun and magazine .dat files. If you are new to caliber concepts entirely, read the Magazine Asset article's caliber linkage section first, then return here for the full ID registry. The Caliber Asset article covers the GUID-based caliber system that is an alternative to the integer ID system documented here.

What you will learn

• What the caliber integer ID system is and how it differs from the GUID-based caliber asset system.
• The full mapping of vanilla caliber IDs to their round designations and representative weapons.
• How the caliber ID links a gun to its compatible magazines through the Caliber and Caliber_Reference fields.
• The special behavior of caliber ID 0 (universal caliber).
• The four caliber categories: Civilian (1), Military (2), Ranger (3), and Improvised (4).
• How multi-caliber guns use Magazine_Calibers and Magazine_Caliber_# to accept magazines of different calibers.
• How attachment compatibility uses the Caliber field independently from magazine compatibility.
• The recommended ID range for custom mod calibers and the collision-avoidance strategy.
• How to verify caliber linkage through in-game testing.
• The most common caliber ID mistakes and how to diagnose and fix them.

Background: the caliber ID as a compatibility key

The caliber ID is a uint16 integer that serves as a compatibility key between a gun and its magazines. There is no central registry authority, no server-side validation, and no runtime enforcement beyond the match-check. Two mods that happen to use the same caliber ID for different rounds will silently accept each other's magazines, producing unintended cross-mod compatibility.

The caliber ID is set in two separate fields on two separate files. The gun declares what it accepts with the Caliber field. The magazine declares what it supplies with the Caliber_Reference field. Both fields must carry the exact same numeric value for the magazine to seat in the gun. There is no wildcard, no range matching, and no fallback behavior beyond the special case of caliber 0.

Caliber ID 0: the universal caliber

Caliber ID 0 is reserved as the universal caliber. A gun with Caliber 0 accepts any magazine regardless of the magazine's Caliber_Reference value. A magazine with Caliber_Reference 0 seats in any gun regardless of the gun's Caliber value.

Condition	Gun Caliber	Magazine Caliber_Reference	Result
Both set to 0	0	0	Magazine accepted (universal-to-universal)
Gun universal, magazine specific	0	5001	Magazine accepted (gun accepts everything)
Gun specific, magazine universal	5001	0	Magazine accepted (magazine fits everything)
Both specific, same value	5001	5001	Magazine accepted (exact match)
Both specific, different values	5001	5002	Magazine rejected (no match)

Caliber ID 0 is useful for test items, admin debug tools, and weapons that are explicitly designed to work with any available ammunition. It should not be used for production mod content that is intended to have controlled magazine compatibility, because caliber 0 on either side opens unintended compatibility with any other caliber-0 item in the game.

The four caliber categories

The Unturned™ caliber system organizes weapons and ammunition into four broad categories that reflect the origin and quality tier of the equipment. These categories are reflected in the vanilla gun set's caliber ID assignments.

Caliber ID	Category	Description
1	Civilian	Weapons and ammunition originating from civilian sources. Typically lower damage and lower range than military equivalents. Common in civilian loot spawns.
2	Military	Weapons and ammunition originating from military stockpiles. Higher damage, range, and durability. Found in military loot zones.
3	Ranger	Weapons and ammunition originating from ranger or survivalist sources. Often intermediate between civilian and military in power, with unique characteristics.
4	Improvised	Weapons and ammunition that are hand-made or fabricated from scrap. Lower reliability, higher wear, and reduced damage compared to factory-made equivalents. Crafted rather than found.

These four categories are the foundation of the Unturned™ loot economy's weapon distribution. Civilian weapons are common in residential and commercial loot spawns. Military weapons are restricted to military zones. Ranger weapons appear in survivalist camps and hunting areas. Improvised weapons are player-crafted or found in workshop and garage areas.

The four categories apply to the caliber asset level

The ItemCaliberAsset class, documented in the Smartly Dressed Games modding documentation Chapter 27, uses the Caliber_# field array to list which calibers an asset is compatible with. The Calibers field sets the count, and each Caliber_# entry holds one caliber ID. The four category IDs (1-4) are the foundational entries in this system, though the actual vanilla gun set uses a broader range of IDs beyond these four.

Complete vanilla caliber ID reference

The table below documents every caliber ID observed in the shipped Unturned™ game files at Bundles/Items/Guns/*/. Each caliber ID is listed with its round designation, representative vanilla weapon, and behavioral notes.

Caliber ID	Round designation	Vanilla weapon(s)	Category	Notes
0	Universal	-	-	Accepts or is accepted by any caliber. Reserved for debug and test items.
1	5.56mm NATO	Eaglefire	Military	Standard assault rifle round. Used by the Eaglefire. Also referenced as Magazine_Caliber_1 on the Augewehr.
3	9mm Parabellum	Colt	Civilian	Standard pistol round. Used by the Colt pistol.
4	9mm Parabellum (SMG)	Cobra	Military	Same 9mm round but used by submachine guns. Cobra and Cobra_Jam use this ID.
6	5.45mm Soviet	Ace	Military	Soviet-pattern intermediate round. Used by the Ace PDW.
8	12 Gauge	Bluntforce	Civilian	Standard shotgun shell. Used by the Bluntforce pump shotgun and the Determinator.
9	9mm Parabellum (SMG alt)	Augewehr	Military	Alternate 9mm SMG caliber ID. Used as Magazine_Caliber_0 on the Augewehr.
12	7.62mm NATO	Dragonfang	Military	Full-power battle rifle round. Used by the Dragonfang.
15	Arrow / Bolt	Crossbow, Bows	Improvised	Archery ammunition. Shared by all bows (Birch, Maple, Pine, Compound) and the Crossbow.
19	.45 ACP	Desert Falcon	Civilian	Heavy pistol round. Used by the Desert Falcon.
23	5.7mm	Avenger	Military	PDW round. Used by the Avenger.
34	4.6mm	Bulldog	Military	Submachine gun round. Used by the Bulldog.
35	5.56mm (alt)	Card	Military	Alternative 5.56mm caliber ID. Used by the Card.
36	Unknown	Ekho	-	Caliber ID observed in game files.
41	Unknown	Empire	-	Caliber ID observed in game files.
42	Energy cell	Bane	Improvised	Energy weapon caliber. Used by the Bane.

Vanilla caliber ID distribution by category

The caliber IDs used in the vanilla gun set do not follow a strict contiguous numbering scheme. The category system (Civilian=1, Military=2, Ranger=3, Improvised=4) provides a conceptual framework, but individual weapons use specific IDs that may fall outside their category's number.

Observed pattern	Explanation
Caliber 1 is used by a military weapon (Eaglefire)	Caliber 1 serves as the military-pattern intermediate rifle round (5.56mm). The category "Civilian" for ID 1 reflects the original intent; in practice ID 1 has been used for military-content rounds.
Caliber 3 is used by a civilian weapon (Colt)	9mm pistol round consistently used by civilian-tier pistols.
Caliber 4 is used by a military weapon (Cobra)	SMG-class weapons use ID 4 for military-pattern 9mm.
Caliber 8 is used by civilian weapons (Bluntforce, Determinator)	Shotgun weapons consistently use ID 8.
Caliber 15 is used by improvised weapons (all bows, crossbow)	Archery weapons form their own caliber family at ID 15, outside the 1-4 scheme.
Caliber 42 is used by an improvised energy weapon (Bane)	Unique energy weapon caliber at ID 42.

How vanilla weapons map to their caliber IDs

The relationship between a vanilla gun and its caliber ID is established in the gun's .dat file through the Caliber field. The table below documents the exact field values observed in the shipped game files, providing modders with a definitive reference for vanilla caliber assignments.

Vanilla weapon	File path (relative to Bundles/Items/Guns/)	Caliber field	Caliber ID
Eaglefire	Eaglefire/Eaglefire.dat	Caliber 1	1
Colt	Colt/Colt.dat	Caliber 3	3
Cobra	Cobra/Cobra.dat	Caliber 4	4
Cobra_Jam	Cobra_Jam/Cobra_Jam.dat	Caliber 4	4
Ace	Ace/Ace.dat	Caliber 6	6
Bluntforce	Bluntforce/Bluntforce.dat	Caliber 8	8
Determinator	Determinator/Determinator.dat	Caliber 8	8
Dragonfang	Dragonfang/Dragonfang.dat	Caliber 12	12
Bow_Birch	Bow_Birch/Bow_Birch.dat	Caliber 15	15
Bow_Maple	Bow_Maple/Bow_Maple.dat	Caliber 15	15
Bow_Pine	Bow_Pine/Bow_Pine.dat	Caliber 15	15
Bow_Compound	Bow_Compound/Bow_Compound.dat	Caliber 15	15
Crossbow	Crossbow/Crossbow.dat	Caliber 15	15
Desert_Falcon	Desert_Falcon/Desert_Falcon.dat	Caliber 19	19
Avenger	Avenger/Avenger.dat	Caliber 23	23
Bulldog	Bulldog/Bulldog.dat	Caliber 34	34
Card	Card/Card.dat	Caliber 35	35
Ekho	Ekho/Ekho.dat	Caliber 36	36
Empire	Empire/Empire.dat	Caliber 41	41
Bane	Bane/Bane.dat	Caliber 42	42

Multi-caliber gun configuration

Some guns can accept magazines of multiple calibers. This is configured through the Magazine_Calibers field (the count of additional calibers) followed by Magazine_Caliber_# fields (the individual caliber IDs).

The Augewehr is the primary example of a multi-caliber gun in the vanilla set:

Magazine_Calibers 2
Magazine_Caliber_0 9
Magazine_Caliber_1 1

With this configuration, the Augewehr accepts magazines with Caliber_Reference matching either 9 or 1. Magazines with caliber 9 are the standard 9mm SMG magazines; magazines with caliber 1 are the 5.56mm NATO magazines (shared with the Eaglefire). This allows the Augewehr to accept a broader set of magazines than a single-caliber gun.

The multi-caliber system is distinct from the single Caliber field. When Magazine_Calibers is present and greater than 0, the engine reads the Magazine_Caliber_# entries and checks the magazine's Caliber_Reference against each one. If any entry matches, the magazine is accepted. If none match, the magazine is rejected, regardless of the Caliber field's value.

The Augewehr is the only vanilla gun that uses the multi-caliber system. Custom gun mods can use the same technique to enable broad magazine compatibility across a weapon family. The Magazine_Calibers value must equal the number of Magazine_Caliber_# fields that follow. If the count and the number of fields do not match, the engine's behavior is undefined - the field should always be kept consistent.

How calibers link guns and magazines

The caliber linkage between a gun and its magazines is implemented through two fields that must carry matching values.

Gun side: the Caliber field

Field	Type	Location	Purpose
Caliber	uint16	Gun .dat	Declares the caliber ID the gun accepts. The magazine must have a matching Caliber_Reference to be accepted.
Magazine_Calibers	uint8	Gun .dat	Optional. The number of additional caliber IDs the gun accepts, specified in Magazine_Caliber_# fields.
Magazine_Caliber_#	uint16	Gun .dat	Optional. Individual caliber IDs the gun accepts in addition to (or instead of) the Caliber field value.

Magazine side: the Caliber_Reference field

Field	Type	Location	Purpose
Caliber_Reference	uint16	Magazine .dat	Declares the caliber ID the magazine supplies. Must match the gun's Caliber field (or one of its Magazine_Caliber_# values) to be accepted by the gun.

Authoring caliber linkage in a custom mod

For a standard single-caliber gun with one magazine variant, the caliber linkage configuration is minimal:

Gun .dat:

Caliber 5001
Magazine 5002

Magazine .dat:

Caliber_Reference 5001

The values must match exactly. A common authoring error is to set the gun's Caliber to 5001 and the magazine's Caliber_Reference to 50001 (one too many zeros). The engine does not warn about the mismatch - the magazine simply does not seat in the gun.

For a weapon family with multiple magazine variants, all magazines share the same Caliber_Reference:

Gun .dat:

Caliber 5001
Magazine 5002
Magazines 2
Magazine_0 5003
Magazine_1 5004

Standard magazine .dat:

Caliber_Reference 5001

Extended magazine .dat:

Caliber_Reference 5001

Armor-piercing magazine .dat:

Caliber_Reference 5001

All three magazines share Caliber_Reference 5001. The gun accepts all three because its Caliber field carries the same value. No additional configuration is needed on the magazine side.

Caliber and the attachment system

The caliber ID also gates barrel attachment compatibility, though through a different field pairing than the magazine system.

Compatibility type	Gun field	Other asset field	Match rule
Gun-to-magazine	Caliber	Caliber_Reference	Exact numeric match
Gun-to-barrel	Caliber	Caliber	Exact numeric match
Gun-to-sight	Slot-based	Slot-based	Sight slot name must match
Gun-to-grip	Slot-based	Slot-based	Grip slot name must match
Gun-to-tactical	Slot-based	Slot-based	Tactical slot name must match

For barrel attachments, both the gun and the barrel attachment carry a Caliber field (not Caliber_Reference). A gun with Caliber 4 accepts barrel attachments with Caliber 4 or Caliber 0 (universal). The barrel attachment's Caliber field uses the same numeric namespace as the magazine's Caliber_Reference field - if a mod uses caliber ID 5001 for its magazine system, barrel attachments intended for that weapon family should also use 5001.

The attachment and magazine compatibility systems use the same field name (Caliber) on the gun side but different field names on the other asset's side (Caliber_Reference for magazines, Caliber for attachments). This naming asymmetry is a common source of confusion. The rule to remember is: the magazine always uses Caliber_Reference to declare what it is, while the attachment uses Caliber to declare what it is compatible with.

Caliber compatibility matrix

The compatibility matrix below shows which caliber IDs are compatible with each other under the standard match rules.

Caliber ID	Accepts magazines with Caliber_Reference	Compatible barrel attachments with Caliber
0 (universal)	Any value	Any value
1	1 or 0	1 or 0
3	3 or 0	3 or 0
4	4 or 0	4 or 0
6	6 or 0	6 or 0
8	8 or 0	8 or 0
9	9 or 0	9 or 0
12	12 or 0	12 or 0
15	15 or 0	15 or 0
19	19 or 0	19 or 0
23	23 or 0	23 or 0
34	34 or 0	34 or 0
35	35 or 0	35 or 0
36	36 or 0	36 or 0
41	41 or 0	41 or 0
42	42 or 0	42 or 0
5001 (custom example)	5001 or 0	5001 or 0

Each caliber ID is an independent compatibility domain. A caliber 4 magazine will not seat in a caliber 8 gun. A caliber 15 magazine will not seat in a caliber 19 gun. The only crossing between domains is through caliber 0, which bridges all domains.

For multi-caliber guns using Magazine_Calibers, the compatibility is expanded. The Augewehr with Magazine_Calibers 2, Magazine_Caliber_0 9, Magazine_Caliber_1 1 accepts magazines with Caliber_Reference 9 or 1 or 0. This is equivalent to a logical OR across the listed caliber IDs plus the universal caliber 0.

Caliber ID collision risks

Because the caliber ID namespace is unmanaged, two independently authored mods can assign the same caliber ID to unrelated rounds. When both mods are loaded on the same server or client, the unintended consequence is that mod A's gun will accept mod B's magazine if their caliber IDs happen to match.

Collision severity by ID range

ID range	Collision risk	Recommendation
0	Universal	Reserved. Do not use for content intended to have controlled compatibility.
1-999	High (vanilla range)	Already assigned to vanilla weapons. Using these IDs for mod content will cause cross-compatibility with vanilla guns.
1000-49999	Medium (established community range)	Used by existing community mods. May collide with another mod on the same server.
50000-65535	Low (recommended custom range)	Less likely to collide with existing content. The 57 Studios™ recommended range for all custom mod caliber IDs.

The 57 Studios™ cohort recommendation is to assign caliber IDs in the 50000-65535 range for all custom mod content. This range is well above the vanilla IDs and aligns with the recommended item ID range for community mods. A mod that uses caliber ID 50001 for its gun-magazine family is unlikely to collide with any other mod on the same server.

Collision avoidance strategy for mod series

For a mod series containing multiple guns across multiple releases, the cohort-recommended strategy is to allocate a caliber ID block and to reuse the same block across all releases.

Mod series: "57 Studios Custom Arms Pack"
Item ID range: 50000-50999
Caliber ID allocation:

  Caliber 50001 → 5.56mm NATO (used by rifles and carbines)
  Caliber 50002 → .308 Winchester (used by DMRs and sniper rifles)
  Caliber 50003 → 9mm Parabellum (used by pistols and SMGs)
  Caliber 50004 → 12 Gauge (used by shotguns)

Each caliber ID covers one round type across all guns in the series. A caliber 50001 magazine works in any 50001 gun within the series. This creates a coherent ammunition ecosystem without cross-contamination with vanilla weapons or other mod series.

Caliber ID assignment checklist

Use this checklist when assigning a caliber ID to a new custom weapon.

• [ ] The caliber ID is not 0 unless the weapon is intentionally universal.
• [ ] The caliber ID is not in the 1-999 range unless the weapon is intentionally compatible with vanilla weapons.
• [ ] The caliber ID is in the 50000-65535 range for a custom mod without vanilla compatibility intent.
• [ ] The caliber ID is unique within the mod project (no two guns in the project use the same ID for different rounds unless multi-caliber is intended).
• [ ] The gun's Caliber field matches the magazine's Caliber_Reference field exactly (same numeric value, no off-by-one errors).
• [ ] If the gun uses Magazine_Calibers, the count matches the number of Magazine_Caliber_# fields.
• [ ] Barrel attachments intended for the gun use the same caliber ID in their Caliber field.

Caliber ID troubleshooting table

Symptom	Most likely cause	Resolution
Magazine does not seat in gun	Caliber_Reference on magazine does not match Caliber on gun	Open both .dat files side by side; confirm the values are identical
Magazine seats in the wrong gun (cross-mod contamination)	Caliber ID collision - another mod uses the same ID	Change one mod's caliber ID to a different value in the 50000+ range
Magazine seats in every gun	Magazine has Caliber_Reference 0 (universal)	Assign a specific caliber ID in the 50000+ range
Gun accepts every magazine	Gun has Caliber 0 (universal)	Assign a specific caliber ID in the 50000+ range
Barrel attachment does not snap onto gun	Attachment's Caliber field does not match gun's Caliber field	Match the values; note that barrel attachments use Caliber not Caliber_Reference
Magazines from one mod work with guns from another mod on the same server	Both mods use the same caliber ID	Change one mod's caliber ID to a value that does not collide
Multi-caliber gun does not accept one of the intended magazines	Magazine_Caliber_# does not include that magazine's Caliber_Reference	Add the missing caliber ID to the Magazine_Caliber_# list and update Magazine_Calibers
Modified caliber ID does not take effect	Game cached the old .dat file	Restart the game or clear the asset bundle cache

Best practices

• Always test caliber linkage by spawning both the gun and the magazine and confirming the magazine seats before testing any other aspect of the weapon.
• Document the mod's caliber ID in the Workshop description so that other modders know which IDs are in use and can avoid collisions.
• Use a single caliber ID for all magazines intended for a single gun family. A standard magazine, an extended magazine, and a drum magazine for the same gun should all share the same Caliber_Reference.
• Avoid caliber ID 0 on production content. Universal caliber is useful for debug items and admin tools but creates unintended compatibility with any other caliber-0 item on the server.
• When updating a mod that changes the caliber ID, inform the community if the change breaks compatibility with existing magazines. A caliber ID change is a save-breaking update that renders all existing magazines of the old ID unusable.
• For a multi-gun mod series, allocate caliber IDs in blocks and do not reuse the same ID for different round types within the series.
• Keep a local registry file (a simple text or spreadsheet document) that maps each caliber ID in the mod to its round designation, intended gun family, and the date of assignment. This prevents internal collision within a large mod project.

Frequently asked questions

What is the difference between Caliber and Caliber_Reference?

Caliber is the field on the gun's .dat file that declares what caliber ID the gun accepts. Caliber_Reference is the field on the magazine's .dat file that declares what caliber ID the magazine supplies. Both fields must carry the same numeric value for the magazine to seat in the gun. The naming asymmetry is a historical convention in the Unturned asset system - the gun uses the short name Caliber, and the magazine uses the qualified name Caliber_Reference.

Can I use the same caliber ID for both magazines and barrel attachments?

Yes. The caliber ID namespace is shared between the magazine compatibility system and the barrel attachment compatibility system. A gun with Caliber 5001 accepts both magazines with Caliber_Reference 5001 and barrel attachments with Caliber 5001. The same numeric value serves as the compatibility key for both systems.

What happens if I change a caliber ID after publishing a mod?

Existing magazines of the old caliber ID become incompatible with the updated gun. If the gun's Caliber changes from 5001 to 5002, old magazines with Caliber_Reference 5001 will not seat in the updated gun. Players who have old magazines in their inventory or storage will need to acquire new magazines with the updated caliber ID. A caliber ID change is a save-breaking update and should be clearly communicated in the Workshop changelog.

Can a magazine be compatible with multiple guns of different calibers?

No, not through the caliber system alone. A magazine has a single Caliber_Reference field, which can match only one gun Caliber value (or be 0 for universal). If the magazine should be compatible with guns of different calibers, the workaround is to set the magazine's Caliber_Reference to 0 (universal), which makes it compatible with all guns. This is the only way to achieve multi-gun compatibility for a single magazine.

How do I find what caliber ID a vanilla gun uses?

Open the vanilla gun's .dat file at Bundles/Items/Guns/<GunName>/<GunName>.dat and read the Caliber field. The value is a plain integer on its own line. The reference table in this article covers all vanilla guns, but always verify against the shipped files if the installation has been updated since this article was published.

Is caliber ID 0 safe to use for a mod that controls its own compatibility?

No. Caliber ID 0 on the gun side opens the gun to accept any magazine on the server, including magazines from other mods and from vanilla content. Caliber ID 0 on the magazine side opens the magazine to be accepted by any gun, including guns from other mods. Use caliber 0 only for test items, admin debug tools, and weapons that are explicitly designed for universal ammunition compatibility.

How do I make a gun that accepts multiple magazine types of different calibers?

Use the Magazine_Calibers system. Set Magazine_Calibers to the number of additional calibers and list each with Magazine_Caliber_0, Magazine_Caliber_1, etc. The gun will accept any magazine whose Caliber_Reference matches any of the listed values, plus any magazine with Caliber_Reference 0. See the Augewehr example earlier in this article.

Why does my mod gun accept a vanilla magazine?

The most likely cause is that the gun's Caliber field matches the vanilla magazine's Caliber_Reference field. If the mod gun uses Caliber 1 and the vanilla Eaglefire magazine uses Caliber_Reference 1, the mod gun will accept the vanilla magazine. Set the mod gun's Caliber to a value in the 50000-65535 range to avoid vanilla compatibility.

Are caliber IDs case-sensitive?

No. Caliber IDs are integers (uint16). There is no case sensitivity in numeric values. The fields Caliber, Caliber_Reference, and Magazine_Caliber_# all accept unsigned 16-bit integers in the range 0 to 65535.

Can I use negative numbers for caliber IDs?

No. The uint16 type is unsigned. A negative value or a value above 65535 will be rejected by the parser or silently truncated. The valid range is 0 to 65535 inclusive.

Is there a registry or authority for caliber ID assignments?

No. There is no central registry, no server-side authority, and no reserved-ID list for caliber integers. The community convention is to use IDs in the 50000-65535 range for custom mod content, but this is a voluntary practice, not an enforced rule. The only way to confirm that a caliber ID is not used by another mod on a given server is to coordinate with the server's mod list.

How do I diagnose a caliber mismatch in-game when there is no error message?

Spawn the gun with @give <gunID> and the magazine with @give <magazineID>. Open the inventory. Drag the magazine to the gun's ammo slot. If the magazine refuses to seat, the caliber values do not match. Open both .dat files, find the Caliber field on the gun and the Caliber_Reference field on the magazine, and confirm they carry the same numeric value. This is the only reliable diagnostic method because the engine produces no error message, no log entry, and no visual indicator for a caliber mismatch.

What is the relationship between this article and the Caliber Asset article?

This article (Caliber ID Registry) documents the integer caliber ID system - the numeric compatibility keys that link guns to magazines. The Caliber Asset article documents the GUID-based caliber asset system - a separate system in which a caliber is a first-class asset with its own .dat file, GUID, and ballistic parameter set. The two systems coexist in Unturned™ modding. Integer caliber IDs are simpler to configure and are the dominant system for single-gun mods and small weapon families. GUID-based caliber assets are more flexible for large weapon packs that need shared ballistic parameter sets across many guns.

How does caliber compatibility work on dedicated servers?

Dedicated servers use the same caliber matching logic as single-player. There is no server-side override for caliber compatibility. If a mod gun and mod magazine have matching caliber values on the client, they will match on the server as well. Caliber compatibility is determined entirely by the .dat file values at load time and is replicated to the server as part of the asset synchronization process.

Appendix A: Vanilla caliber ID quick-reference card

ID	Round	Representative weapon	Category
0	Universal	-	-
1	5.56mm NATO	Eaglefire	Military
3	9mm	Colt	Civilian
4	9mm SMG	Cobra	Military
6	5.45mm	Ace	Military
8	12 Gauge	Bluntforce	Civilian
9	9mm SMG alt	Augewehr	Military
12	7.62mm	Dragonfang	Military
15	Arrow/Bolt	Crossbow	Improvised
19	.45 ACP	Desert Falcon	Civilian
23	5.7mm	Avenger	Military
34	4.6mm	Bulldog	Military
35	5.56mm alt	Card	Military
36	Unknown	Ekho	-
41	Unknown	Empire	-
42	Energy	Bane	Improvised

Appendix B: Custom caliber ID allocation worksheet

Use this table to plan caliber ID assignments for a new mod series before authoring any .dat files.

Caliber ID	Round designation	Intended gun family	Number of magazine variants	Notes
50001	5.56mm Custom	Assault Rifle + Carbine	3 (standard, extended, drum)	Primary round for the weapon series
50002	.308 Custom	DMR + Sniper	2 (standard, extended)	Precision round
50003	9mm Custom	Pistol + SMG	2 (standard, extended)	Sidearm round
50004	12 Gauge Custom	Shotgun	2 (standard, slug)	Shotgun round

Fill in the worksheet before authoring to ensure that caliber IDs are consistent across all weapons in the series. A filled worksheet prevents the common mistake of assigning different caliber IDs to what should be the same round across different guns in the same series.

Appendix C: Caliber ID field syntax reference

Single-caliber gun

Caliber 5001
Magazine 5002

Multi-caliber gun

Caliber 5001
Magazine 5002
Magazine_Calibers 2
Magazine_Caliber_0 5001
Magazine_Caliber_1 5003

Standard magazine

Caliber_Reference 5001
Amount 30

Barrel attachment (same caliber namespace)

Caliber 5001

Appendix D: Caliber ID categories detail

The four caliber categories (Civilian, Military, Ranger, Improvised) serve as the foundational classification for the Unturned™ loot economy. The table below provides the detailed characteristics of each category.

Category	Caliber ID	Loot location	Typical damage tier	Typical durability	Craftable?
Civilian	1	Residential, commercial, farming	Low to medium	Low to medium	No
Military	2	Military bases, bunkers, airdrops	Medium to high	Medium to high	No
Ranger	3	Hunting camps, survivalist caches, National Park zones	Medium	Medium	Sometimes
Improvised	4	Workshops, garages, player crafting	Low	Low to medium	Yes

Category ID 1 (Civilian) is used by weapons that spawn in civilian loot tables and are typically the first weapons a player encounters. Category ID 2 (Military) covers weapons found in restricted-access military zones. Category ID 3 (Ranger) covers the survivalist and hunting weapon tier, which is intermediate between civilian and military in availability and power. Category ID 4 (Improvised) covers weapons that are primarily player-crafted, such as bows and the makeshift energy weapon.

The actual caliber IDs used in the shipped game files extend well beyond these four categories. The four IDs represent the original conceptual framework of the caliber system; the game's actual weapons use a wider range of IDs to accommodate specific round types that do not fit neatly into a single category.

Appendix E: Caliber ID discovery procedure

When encountering an unknown caliber ID in a mod or in updated game content, use the following procedure to determine its round designation:

1. Open the gun's .dat file and read the Caliber field value.
2. Open the paired magazine's .dat file and read the Caliber_Reference field value.
3. If the two values match, the caliber ID is the one shared between them.
4. Search the vanilla Bundles/Items/Guns/ directory for other guns that use the same Caliber value. Each match is a weapon that shares this caliber.
5. Search the vanilla Bundles/Items/Magazines/ directory for magazines with the same Caliber_Reference value.
6. Examine the gun that uses the caliber - its round designation (5.56mm, 9mm, 12 gauge) can often be inferred from the weapon's real-world counterpart or its in-game description.
7. Document the finding in the Workshop changelog or a local reference file so that other modders can avoid accidental collisions.

Appendix F: Cross-mod caliber compatibility scenarios

The following scenarios illustrate common cross-mod caliber compatibility situations.

Scenario 1: Two mods, no compatibility intended

Mod A uses caliber 50001 for a 5.56mm assault rifle. Mod B uses caliber 50002 for a .308 sniper rifle. The two mods have no unintended compatibility because their caliber IDs differ. A player can carry both mods without any magazine-cross-contamination issues.

Scenario 2: Two mods, unintended compatibility

Mod A uses caliber 50001 for a 5.56mm assault rifle. Mod B also uses caliber 50001 for a 9mm SMG (the mod author was unaware the ID was already taken). When both mods are loaded, Mod A's assault rifle accepts Mod B's SMG magazines because both use caliber 50001. The SMG's 9mm magazine appears to function in the 5.56mm assault rifle, which produces confusing in-game behavior. The fix is for one of the mod authors to change their caliber ID.

Scenario 3: A mod designed for vanilla compatibility

A mod author wants to create a high-capacity drum magazine for the vanilla Eaglefire (caliber 1). The drum magazine sets Caliber_Reference 1. The drum magazine is accepted by the Eaglefire and by any other gun (vanilla or mod) that uses caliber 1. The mod author must accept that the drum magazine is also compatible with any other mod gun that uses caliber 1.

Scenario 4: A weapon family across multiple mod releases

A mod series releases three guns across three months. All three guns use caliber 50001. The magazines from the first release are compatible with the guns from the second and third releases. Players who bought the first release can use its magazines in the later guns without purchasing additional magazines. This is the intended behavior for a coherent weapon family.

Authoring checklist

Before publishing a new gun mod with caliber linkage, confirm the following:

• [ ] The caliber ID is in the intended range (vanilla 0-999, or custom 50000-65535).
• [ ] The gun's Caliber field matches every magazine's Caliber_Reference field.
• [ ] The gun's Magazine_Calibers count (if used) matches the number of Magazine_Caliber_# fields.
• [ ] Barrel attachments for the gun use the same caliber ID in their Caliber field.
• [ ] The caliber ID does not collide with any other mod that will be used on the target server (verify with the server admin if deploying to a known server).
• [ ] The caliber ID is documented in the mod's Workshop description.
• [ ] The caliber linkage is tested in single-player before the mod is published.
• [ ] If changing a caliber ID from a prior release, the changelog clearly states that the change breaks magazine compatibility with the previous version.

Document history

Version	Date	Author	Notes
1.0	2026-07-26	57 Studios	Initial publication. Complete caliber ID registry covering all vanilla IDs, category mapping, compatibility rules, custom ID conventions, and cross-mod collision guidance.

Cross-references

• Weapon Asset Reference - the previous article; covers the ItemWeaponAsset base class fields used by all weapons including caliber-linked firearms.
• Caliber Asset - covers the GUID-based caliber asset system, ballistic parameters, damage falloff, and the distinction between integer and GUID caliber linkage.
• Magazine Asset - covers the magazine .dat structure including Caliber_Reference and the damage multiplier fields that interact with caliber values.
• Gun Mod Tutorial - the end-to-end gun mod tutorial that covers caliber configuration as part of the .dat authoring step.
• Arrest Start Asset Reference - the next article in the items section.
• Smartly Dressed Games modding documentation - official field definitions for the caliber asset system.
• Unturned on Steam - the game's Steam store page and update changelog.