Weapons database
MW4 Attachments: Categories, Unlocks & Compatibility
Understand standard slots, shared unlocks and Apex exclusions before spending time on a build.
Attachment categories
M4 and Han 86 list nine base categories: Optic, Muzzle, Barrel, Underbarrel, Magazine, Rear Grip, Stock, Laser and Ammunition. Other weapons may substitute Comb, Bolt, Guard, Trigger Action or Fire Mods. A category name does not prove that every attachment in it fits every weapon.
Unlock once, use where compatible
A shared compatible attachment only needs to be unlocked once. Each weapon can unlock its own supported set; another weapon is not required just to complete that set. An attachment already owned can trigger a Bonus Level Up in the weapon track. Weapon Prestige changes this behavior for the chosen weapon, so review the Prestige rules first.
Apex and blocked slots
Apex uses its own slot, but it can disable normal categories. M4 Hurricane blocks Barrel and Magazine; Han X20 Skybreaker blocks Optic, Stock and Barrel. Check the converted weapon before trying to restore an incompatible standard attachment. For the mechanism and Gunny suggestions, read Gunsmith & Apex.
Sources & version
Source review: October 22, 2026. Official equipment guide · Weapon Prestige update