Firearms can be customized with modifications that alter their function, handling, electronics, accessories, or other capabilities.
Each firearm belongs to a Frame that determines which modification slots it has. Each available slot can hold one modification.
Having the correct slot does not automatically mean a modification is compatible. Individual modifications list any Frame requirements, weapon requirements, installation procedure, and other restrictions that apply.
Purely cosmetic changes do not normally use modification slots unless they provide a mechanical benefit.
Firearm Frames
Every firearm belongs to one of three Frames. A firearm’s Frame determines which modification slots it has.
| Frame | Internal | Top | Bottom | Muzzle | Stock |
|---|---|---|---|---|---|
| Small | ✓ | ||||
| Handgun | ✓ | ✓ | ✓ | ✓ | |
| Full-Size | ✓ | ✓ | ✓ | ✓ | ✓ |
Each firearm has one slot of each type shown for its Frame.
Small firearms include holdouts and similarly compact designs.
Handgun firearms include pistols, revolvers, machine pistols, and similar weapons.
Full-Size firearms include SMGs, shotguns, rifles, machine guns, and similar weapons.
A firearm’s individual entry may override its normal Frame when its construction requires it.
Modification Slots
Firearm modification slots represent the part of the weapon being altered or fitted with additional equipment.
Internal: Changes to the firearm’s internal mechanisms, electronics, feed system, fire-control system, or similar components.
Top: Optics and sighting systems such as scopes, reflex sights, thermal optics, smart optics, and rangefinders.
Bottom: Underbarrel and accessory equipment such as flashlights, lasers, foregrips, bipods, and secondary weapons. Side-mounted accessories normally use the Bottom slot as well.
Muzzle: Devices fitted to or modifying the muzzle, such as suppressors, compensators, muzzle brakes, and flash suppressors.
Stock: Stocks and rear assemblies such as folding, adjustable, precision, or recoil-reducing stocks.
A modification normally occupies one slot.
Installing a new modification in an occupied slot requires removing the existing modification first.
Mod Compatibility
Having the correct modification slot does not automatically mean a mod fits every firearm.
Each modification lists the Frames it can be installed on and any additional requirements that apply.
Common requirements may include:
- Handgun or Full-Size Frame only.
- Automatic firearm required.
- Detachable magazine required.
- Compatible ammunition feed required.
- Specific slot or weapon feature required.
Compatibility is handled by the individual modification rather than by adding more slot types or variable slot costs.
A firearm may therefore have an available slot but still be unable to accept a particular modification.
Installing and Removing Mods
Each firearm modification lists its installation requirements and installation time.
Simple Installation: Mods designed to be fitted or removed without specialized work require no test. Spend the listed installation time.
Armorer Installation: Mods that alter the firearm’s internal mechanisms, electronics, feed system, structure, or other complex components require an Armorer test. Spend the listed installation time, then make the test.
On a failed test, the installation fails and the time is spent.
A Complication may cause additional problems such as damaged components, lost parts, poor calibration, or damage to the firearm.
Removing a modification follows the same general procedure. Simple mods can normally be removed without a test, while integrated or complex modifications may require Armorer.
Cosmetic Changes
Purely cosmetic alterations do not use modification slots.
Examples include paint, engraving, decals, decorative finishes, grip wrapping, and cosmetic lighting.
If a change provides a meaningful mechanical benefit, it is treated as a modification and must use an appropriate slot.