Weapon Modifications are unlockable attachments in PAYDAY 2 that can be installed on a weapon, and will affect the stats of that weapon. The stat effects may be positive or negative, and most modifications have a mixture of positive and negative effects on the various different stats, though some mods have purely positive (or rarer still, purely negative) effects.
Any installed modifications will also be visible on the Item Preview in the Inventory, as well as on the in-game appearance of the weapon; mods installed in the Sights slot, especially, will alter the gunsight when aiming.
Some Weapon Modifications are only compatible with one particular weapon, while others are compatible with multiple weapons/weapon types. In general, barrel extensions, sights and gadgets are compatible with many weapons, while other mods are restricted to a single weapon or a weapon family (e.g. the AK family, comprising the AK, the AK.762, the Golden AK.762, the Krinkov, the IZHMA 12G, and the RPK).
There are six ways to unlock weapon modifications :
- Drawing a weapon modification card (showing two crossed rifles) during a payday.
- Modifications obtained through payday card drops will cost money (from spending cash) to fit to a weapon and your stock of them is limited to the number of times you have drawn that card. If you have two of a given card-drop modification "in stock" (weapon modification not fitted to a weapon) then you will no longer be able to obtain that card during a payday. Note that this can be exploited when farming cards - some players will remove all the card-drop mods from weapons they aren't using in order to force the card drop RNG to choose a different modification which they do not have.
- Completing a Gage courier package assignment, available to owners of the Gage Mod Courier DLC only.
- Modifications obtained through collecting courier packages will cost no money at all to fit to a weapon, allowing easy experimentation, particularly with weapon sights. Your stock of them is limited to the number of times you have received each weapon crate (for collecting the required number of each package type) but, unlike card-drop modifications, there is no limit to the number you may have in stock.
- Unlocking certain achievements, available to the respective DLCs' owners only.
- Modifications obtained through achievements will cost money (from spending cash) to fit to a weapon. However the stock of them is infinite, allowing you to fit them to as many weapons as you like without having to repeat the achievement or draw cards.
- Bonus mods from DLC
- Most recent DLC packages give one of each mod present in that DLC to players upon purchase of said DLC. Some mods are even available in infinite stock (most notably Ammunition).
- Completing Side Jobs, and selecting a mod
- When you complete a daily job, you are presented with 20k spending cash, and a weapon mod of your choice. You are able to select which weapon the mod is for, and what DLC it is from (provided it is unlocked via card drop). You also have the option to select a community-made item, or a base game item.
- Purchasing them with Continental coins
Once fitted, modifications can be removed free of charge and will be returned to your stock. However, there is no refund for doing so, therefore removing and reinstalling Modifications repeatedly will cause loss of spending cash. Generally this is the reason why players often simply purchase and keep differently modified versions of the same weapon to complement different builds.
As modifications obtained through Gage courier rewards are free to fit to a weapon, they are free to experiment with, which is particularly useful when trying to find a sight that you like.