Gun customization is a feature that appears in Metal Gear Solid 4: Guns of the Patriots and Metal Gear Solid V: The Phantom Pain. In the latter, once unlocked by finishing the 3 legendary gun smith side missions, unlocked after mission 13, the player can modify guns in their ACC. The more guns the player has, the more parts they can use to customize.
Attachment Type Overview
| Part Name | Overview |
|---|---|
| Base | The base firearm, on which attachments are fixed. |
| Barrel | Applies modifiers to firing speed, Effective range, Grouping and auto-aim Correction specs. |
| Magazine | Modifies the capacity of each magazine, as well as the weapons maximum stock of ammo. |
| Stock | Applies modifiers to the weapons stability when aiming while moving, and the time it takes before the player can again aim after firing. |
| Muzzle | Determines what type of accessory can be attached to the muzzle. |
| Muzzle Accessory | Reduces tremor (therefore improving grouping) and can enable the attachment of a noise surppressor. |
| Optics 1 | Enables the attachment of a scope, or a combination of small scope parts. This can provide dot sights or magnification levels. |
| Optics 2 | Available if a second scope part can be combined with the first part. |
| Flash Light | Improves visibility at night, and can blind enemies that you aim at. |
| Laser Sight | Improves aiming accuracy. |
| Underbarrel | Enables the attachment of a foregrip, which reduces the firing tremor while moving and the aiming speed. With the assault rilfes and certain sniper rilfes, the player can instead equip them with underbarrel handguns, shotguns and grenade launchers. |