Gun attachments and maintenance in Project Zomboid

Weapon parts are fitted from the gun, not from the part. You need three things in your main inventory or an open bag: a compatible gun, an unbroken part and, for most parts, an unbroken screwdriver. See tools if you do not have one yet.

1. Right-click the gun.
2. Choose Upgrade, then pick the part.
3. To take a part off, right-click the gun, choose Remove Upgrade and pick the installed part. Removal uses the same tool as fitting.

Ammo Straps and the Gun Light go on by hand with no screwdriver. A broken gun can still take parts, and the parts come back to you if that gun is later used up as a repair donor.

If Upgrade does not appear, check four things: the gun does not accept that part, the slot is already full, the screwdriver is missing or broken, or the part is in a container you cannot reach.

Each gun has up to four slots, and each slot holds one part. This is why you cannot stack a laser and a gun light on the same pistol, or a choke and anything else on a shotgun barrel.

The figures below come from one detailed Build 42.19 breakdown (one source) and match the in-game tooltips we could see. Scope sight values replace the gun's own minimum and maximum sight range rather than adding to it. A negative aim time means the gun comes up faster. For the guns themselves, see firearms.

The vanilla Laser Sight does not draw a visible beam. It is a stat bonus only. The Gun Light needs a battery and lights the area in front of you, which helps at night (see lighting).

Build 42 has no vanilla suppressor. Every silencer or suppressor you see in videos comes from a Workshop mod, and the well-known ones were written for Build 41 with no confirmed Build 42 support. Firing a gun stays loud, so plan for the noise drawing zombies from a wide area.

There is also no vanilla bayonet, separate sling item, iron sight part or fiberglass stock in 42.19. The Sling slot exists, but only Ammo Straps go in it. Large gun packs on the mods page add many of these parts.

Opinion On a rifle you plan to use near zombies, a Red Dot or Laser beats a long scope, because faster aim matters more at short range. Save the x4 and x8 for a hunting or overwatch rifle. On shotguns, the Full choke plus Ammo Straps is the most useful pair.

Every gun has a condition bar that wears down with use. When it reaches zero the gun is broken and cannot fire until repaired. Condition carries over when you swap parts, so a mint scope on a worn rifle does not help reliability.

Jamming is a sandbox setting. The Indie Stone's Apocalypse preset turns firearm jamming on, and you can switch it off in sandbox settings. Early Build 42 versions drew many player complaints about pistols jamming even in good condition, and later patches eased jamming through sandbox multipliers. Players widely link jams to low condition, but we could not find a confirmed formula for Build 42.

When a gun jams, rack it to clear the jam before firing again (in Build 41 the reload key did this). Do not count on a single gun in a crowd.

Opinion Carry a melee backup from best weapons and keep spare guns of the same model, since they double as repair parts.

Vanilla guns are not fixed with duct tape, glue or a repair kit. Instead you combine two guns: right-click the damaged gun and pick Repair, using a donor gun of the same family. The donor is destroyed, but its parts, magazine and loaded rounds go back into your inventory. Aiming skill sets who can do it (see skills).

The first repair restores about 50% of missing condition, the second about 20% and later ones about 10% (one source). Each Aiming level above the requirement adds about 5%, up to 25%, and lowers the failure chance, which is about 5% at the minimum level. Each repaired gun gets less from later repairs, so a gun repaired many times is worth replacing. Find donors through gun locations and military bases.

There is no vanilla cleaning action or cleaning kit in Build 42. Cleaning kits, rust and dirt systems come from mods. To keep loaded guns useful, also stock rounds via ammo crafting.