Before talking about Weapon Penetration values, we need to talk about Object Thickness first.
These values apply to every object in the game, from walls to tables, fences and even players.

If your weapon penetrates multiple objects, like say through an arcade cabinet and then through a wall, their values are combined when calculating penetration. To be safe, I would recommend considering an object to be one thickness tier higher when there is another object behind it.

For example, if you shoot through lockers on Killhouse that have a wooden wall behind them, they will have a thickness value between Thick and Very Thick. Consider this penetration Very Thick to be safe.
Another example are back-to-back metal shelves in Freezer on Cstore. These are both Thin objects, but combined they have a thickness value that is more similar to Thick.

Objects can also have multiple hitboxes, and each hitbox will affect penetration individually.
For example, if you shoot through an arcade cabinet at the wrong angle, your weapon might not penetrate at all, when it would be able to shooting through it at a slightly different angle.

In Due Process there are 4 types of Object Thickness: None, Thin, Thick, Very Thick and Ballistic.

None:
Many objects in the game can be shot through without being considered a penetration. These are usually objects that either need a collision hitbox for other purposes, like breakable glass, or can't be walked through but can be shot through, like fences or toxic tarp.

Thin:
If the object you're shooting through looks flimsy, or is thin and wooden, it's probably Thin.
Some examples of Thin objects are the wooden Killhouse walls, non-metal green doors, and a lot of the small objects/furniture.

Thick:
If the object you're shooting through is thin metal or thick wood, it's probably Thick.
Metal green doors, Players and various objects like Arcade Cabinets and Lockers are Thick.
Cstore Bathroom stalls are Thick.

Very Thick:
Most Very Thick objects are walls, with some exceptions like Fridges on Cstore.
If the walls aren't wooden and aren't an exterior wall, it's probably Very Thick.
Very Thick walls are most walls on Cstore, Factory and Bank.
Killhouse's brick walls and Pillbox doors, and the Freezer doors on Cstore, are Very Thick.

Ballistic:
Ballistic objects are impenetrable.
Many thick metal objects are Ballistic, and all red doors are Ballistic.
For walls, they're usually marked with a black border on top of the wall on the map. Exterior walls are almost all Ballistic, except fences or similar. Cstore Teller glass and Bank Security glass are Ballistic. Killhouse Pillbox walls are Ballistic.

Killdome:
Lastly, almost everything on Dome is Ballistic, even stuff that look like they should be Thin. There are some exceptions, such as interior doors and the castle drawbridge, but for the most part you will not be able to wallbang on Dome.

Now that we've got all that thickness stuff out of the way, time for what the weapons can actually penetrate.
Weapons are categorised into 4 penetration types: High, Medium, Low and Shotguns.

High Pen:
The Snipers, Dawn, Nack and Legros.
These can pen up to 2 Thin objects with full damage, or up to 7 Thin objects with half damage.
They can pen up to 2 Thick objects or 1 Very Thick object with half damage.
I mostly use these on Cstore, Factory and Bank for wallbangs. They can also be very useful on Killhouse for wallbanging through lockers against a wooden wall.

Medium Pen:
The AP-25, BLK-Tar, Ingmar and the KRs.
These can pen 1 Thin object with full damage, and up to 4 Thin objects with half damage.
They can pen 1 Thick object with half damage.
They can't pen Very Thick objects.

Low Pen:
The Grubers and Pistols.
These can pen up to 2 Thin objects with half damage, and lose all damage through any other objects.

Shotguns:
Have slightly worse pen than the low pen weapons, they can only pen 1 Thin object with half damage.

Headshots:
Lastly, if you deal full damage through an object you can also deal headshots. If your damage is halved you can't.

This section will be explaining what I personally choose when setting up wallbangs in most situations. The rest of the guide is mostly objective, just giving you the stats. But this part is obviously going to be much more subjective, based on my experience.

Most wallbang setups will happen on Killhouse, due to the abundance of thin objects. If I see a Killhouse coming up I will try to keep it in mind when choosing my weapons.
I typically avoid shooting through thick objects as your damage is reduced and you can be shot back at by the attackers, but I would choose the same weapons as I would for shooting through thin objects.
Shooting through very thick objects is only good if you can trap the attackers, like in a barb wire or funneled through a narrow passageway. It can take upwards of a full second to kill as your damage is halved, but the Attackers can't shoot back as their weapons are only medium pen or worse, excluding the SABR which has limited ammo.

• For thin objects, like wooden green doors or the wooden walls on killhouse, my go-to choice on Defence is the KRU.
  The KRs have a fantastic TTK (time-to-kill), and when only shooting through a single thin object they will do full damage and retain the ability to headshot. As you will typically be at close to medium range for these wallbangs, the KRU fits this role perfectly.
  
  Other great options are the KRM and Ingmar.
  You only have a single KRM, and it may be needed elsewhere for its great TTK at medium to long range.
  The Ingmar's scope and fantastic headshot TTK makes it great at countering attackers with the SABR or BLKs.
  Both are still worth taking if they feel more appropriate for your specific wallbang setup, or if the KRUs have all been taken.
  
  For Attack, both the AP and BLK are medium penetration, and the SABR is high penetration. So all options are great for thin wallbangs, therefor if you see a Defender's bullet tracers, try to shoot back at where you estimate the bullets are coming from.
  
  
• For very thick objects, like non-wooden walls (Killdomes' walls are not penetrable), freezer and pillbox doors and lockers on killhouse, the Nack is my go-to choice.
  The advantage of shooting through very thick objects as a defender is that the SABR is the only Attacker weapon with high penetration. This means the Attackers can't shoot back, unlike with thin objects.
  The Nack has a TTK of 0.44s, meaning it will kill an Attacker through a very thick wall in 0.88s as high penetration weapons deal half damage through walls. The Nack also has a lowered headshot multiplier of only 1.5x, but this doesn't matter as you can't deal headshots through very thick walls.
  Due to the TTK being quite high, it is very advisable to set up your wallbangs down narrow corridors, or on to barb wire that the Attackers are forced to go through.
  
  The Legros and Dawn are other options for this, but due to their poor TTK, you won't be able to deal much damage with very thick wallbangs. And because both weapons are also generally weak compared to other options, I do not personally setup wallbang strategies with these weapons.
  
  
• For multiple thin objects, the high penetration weapons, the Nack, Legros and Dawn are the best choices for Defence. If you feel confident you can still be accurate with the Nack in your specific setup, I would take that over the others due to its better TTK.
  Attackers do not have a good option for this, the SABR is high penetration but low on ammo. Shooting back with the AP or BLK could be wasteful as you are doing half damage. I would typically avoid shooting back if I know it's through multiple thin walls.
  
  
• I will typically avoid wallbanging with low penetration weapons as they can only deal half damage through thin objects, and the AP and BLK are medium penetration, so the Attackers will have an advantage shooting back at you. The Gruber-SD may be a small exception here, as the suppressor removes bullet tracers. However, you will steal be dealing very little damage through walls.

Wallbangs on Due Process are really strong in the right situations. Generally, if the enemies have to walk through a tight area (a doorway for example), especially if that area is barbed, it's a great opportunity to be ready for a wallbang. If you can listen for sound cues from barbs, or have a teammate watch the area for you, wallbangs become even stronger.

If you're wallbanging on Killhouse, remember that most Attacker weapons can deal full damage right back at you. So be very careful, stay behind heavier cover where possible and try to be sporadic with your wallbang timings. And if you're an Attacker getting wallbanged, shoot back.

21/03/25 - Been a while since I last played, but in that time red doors were all changed to be ballistic, so I have updated the guide accordingly. I also updated the guide for better readability.

09/04/25 - Added a new "summary" section, where I clearly explain how exactly I set up for wallbangs in most scenarios. A lot of this is based on my personal experience, and is very subjective compared to the rest of the guide, which is generally objective.

11/04/25 - Edited some bad or outdated information, most importantly that metal green doors are Thick and Pillbox walls are Ballistic.

14/04/25 - Removed various personal suggestions from the thickness and penetration sections, and moved it all to the summary section. Added thick values to the penetration section. Changed from calling it "Wall Thickness" to "Object Thickness" and edited the guide accordingly, as well as adding a small section on combining object thickness.