Game systems
MW4 Gunsmith & Apex Attachments Explained
Understand shared attachment unlocks, Apex slots, restrictions and Gunny build suggestions.
Shared unlock flow
Gunsmith is available in Multiplayer and the DMZ FOB. A compatible shared attachment is unlocked once; another weapon can use it where compatible. Each gun can unlock its own supported set. If a level reward is already owned, Bonus Level Up advances the weapon track rather than requiring the same attachment grind again.
Apex is separate, compatibility is not unlimited
On supported weapons, the last weapon-level reward is an Apex conversion. It uses a separate slot and does not consume a normal attachment slot. It can still disable specific normal categories. M4 Hurricane blocks Barrel and Magazine; Han X20 Skybreaker blocks Optic, Stock and Barrel. The separate slot is not a promise that every previous attachment remains valid.
Gunny and the Details view
Gunny suggests short-range, balanced or long-range builds using attachments you own. Treat the suggestion as a starting point. Inspect the Details view for the weapon you actually equipped, compare the intended range and recheck the configuration after an Apex or Prestige change. Do not infer a precise TTK from summary bars.
Sources & version
Source review: October 22, 2026. Official Gunsmith explanation · Launch changes