In this guide I will call the two-handed weapons guns and the revolver - well - revolver.

How to get weapon parts?
Weapon parts drop mainly from soldiers which also can drop full guns (with four to seven parts). They can also won as a reward of the slot machine or from magic chests.

What does the color mean?
The color shows the quality of the part. It depicts not exactly rarity, because the lowest tiers drop less to never as the player progresses. There are five tiers (for revolvers only the first two): gray (common), green (uncommon), blue, purple (rare) and yellow (legendary). In general higher tiers are better than the lower ones of the exactly same part, but it seems there are rare exceptions.
The tiers of the gun parts also determine, if you have to repair with scrap or iron ingots.

What should I do with parts I do not need?
I store the best in case i want to try a different play style (though I never do). The rest can be recycled using the recycler. Higher tiers seem to give better recycling rewards.

My guns stats decreased, but i changed no parts!
Weapons lose durability through using them. With decreasing durability the stats also decrease. The can be restored through repair. You can repair them with scrap metal or iron ingots.
Repair your gun always before comparing parts!

There are eight different stats and the dps which seems to be calculated from first four of them.

The damage one bullet (or one shot in case of shotgun) makes.

The rate the weapon fires. Displayed in shots per minute.

lower = better
The time it takes to (standard) reload your gun. Displayed in seconds. I guess the rofleemo reload or the special revolver reloads are unaffected.

higher = better
The number of bullets (shots for shotgun) your weapon can hold.

higher = better
How your shots scatter around the crosshair. If the wiki can be trusted this describes only the hipfire accuracy.

higher = better
How much recoil you have while shooting.

higher = better
The range of the weapon. I don't really know if the bullets disappear after this distance or how it really affects the bullets.

lower = better
How fast your draw or switch to your gun.

The revolver also known as "Old Friend" is your permanent weapon. You can only have one and you cannot unequip it after you pick it up. It has unlimited ammo.

The revolver has three different parts: Barrel, Frame and Grip. They exist only in the lowest two tiers (grey and green).

The stats of the parts are directly linked to their names. However there are slightly better parts with the same name and the same tier. I will only list the stats of second tier parts (because i recycled all of the others; my bad).

The Appearance of the parts seem to have a slight link to the name. For example "Friend" barrels have one Appearance, "Henry" barrels another. But there are exceptions. So you cannot say for sure, what kind of part you have by appearance.

The barrels affect fire rate, accuracy, stability and range. Some barrels have a chance to duplicate a bullet on firing.

There are four barrel types:

• Friend
  
• Splint
  
• Punctual
  
• Henry

These types come with three attributes. These attributes affect only the range.

• Heavy (worst)
  
• Basic
  
• Long (best)

In the following table I list the best stats I found on 'Long' barrels. If I found better stats on other ones, I also list them.
The stats are listed in comparison to the "Basic Friend".

* I haven't got both values on one part.
** These stats seem to have other values in the background that are rounded. I don't know if the numbers in the background or those shown are the final stats of the weapon. Thats why some part combinations show better numbers altough they shouldn't.

The frame affects damage, fire rate, reload speed, magazine size, accuracy and stability. There are no frames with additional properties.

There are six different types of frames:

• Geezer
  
• Pest
  
• Impudence
  
• Service
  
• Boaster
  
• Founder

Frames are divided into two groups, which have similar Stats within their groups.
In the following I compared the "Heavy Frame 'Geezer'" to the "Basic Frame 'Geezer'"

The grip only affects the handling of the revolver. Some grips increase melee damage.

There are three grip categories (from best to worst):

• Flexible - better handling
  
• Basic - average handling
  
• Heavy - worse handling

These three categories can appear combined with two attributes:

• none
  
• Hustler - much better handling
  
• Brawler - much worse handling, up to +100% melee damage

So you should either get a "Flexible Grip 'Hustler'" or a 'Brawler' (best: "Flexible Grip") with high melee damage increase.

Since the grip does not interfere with the barrel or the frame, look above to find the best grip.

The revolver has some stats capped, so using some parts or part combinations cannnot be used to their full potential.

The caps are:

• Damage: 60
  
• Range: 15

The highest stats I managed to get on a revolver are the following (not all with the same parts):

• Fire Rate: 150
  
• Reload Speed 0.8
  
• Magazine Size: 9
  
• Accuracy:74
  
• Stability: 61
  
• Handling: 0.3

DPS = Magazine Size * Damage / (Magazine Size * 60 / Fire Rate + Reload Speed)

The highest DPS I got was 60.4 (with the property of the Henry calculated in 63.4).
Setup: "Long Barrel 'Henry'" + "Basic Frame 'Pest'"
But this setup has a very low stability so, you cannot fire that fast, if the enemy is not directly in front of you.

If you prefer long ranged fights or clearing mines in the distance you could try this:
Setup: "Long Barrel 'Punctual'" + "Basic Frame 'Founder'"
It has a dps of 30.5 (which is very low), but a stability around 60 and a accuracy up to 40. With this you can shoot precisely without having to wait for the gun to come down.

If you like to snipe switch the "Basic Frame 'Founder'" with the "Heavy Frame 'Pest'":
You'll get the full 60 damage and accuracy up to 70. WIth a "Long Barrel" also 14.7 range which is close to the full 15.

Guns are the other kind of weapon. They consist of four to seven gun parts which drop like full guns from enemies. There is no limit to guns you can have, but you can have only two equipped at the same time.

Guns use one of three ammo types which is determined by the guns barrel: Rifle, Hunter or Shotgun.
You have seperate storage slots for every ammo type in your inventory.

There are gun parts (Core) which can add an alternate firing mode to a gun. This alternate firing mode uses the fourth ammo type: Special Ammo

Guns can also have Effects which are applied to enemies by the bullets. Look at the chapter on Gun Effects for more information.

A gun must have the following four parts: barrel, magazine, frame and grip. These exist in all five weapon part tiers.
Stock and Sight can be added and exist only in the lowest two tiers.
The seventh gun part is the Core. It adds one of three alternate firing modes. It has no tiers.

The appearance of parts seems not to be linked to stats or names.

The magazine affects reload speed and magazine size. Every magazine has one magazine property. Magazines can also have an additional gun effect (> Guns - Gun Effects). These magazines have an additional effect property.

The following studies are based on magazins from the highest three Tiers. I will include lower and more someday. Maybe some things appear more clean with more data.

The attributes and names indicate something about the stats, but there are no clear values linked to them. So there can be magazines with seemingly bad attributes/names that are better than some with seemingly good attributes/names. What I analyse are trends.
Also not every name appears in every Tier.

In the following tables I will grade the stats of the attributes and names. Note that this is for the average magazine with that name. There are better ones and worse ones.

Every attribute appears in every Tier.

There are three gun effects:

• Poison/Toxic - deals poison damage over time
  
• Flame/Ignite - deals fire damage over time, ignited soldiers panic*
  
• Ice/Cryo - freezes enemies for some seconds, frozen enemies take more damage*

* Information from Voidtrain-Fandom

The effect is activated on bullet impact on enemy.

They can be on magazines, but they are very rare (I got them mostly from the slot machine I think.
The effect is part of the magazines name.

The effect has two attributes: chance to apply and damage. The damage seems to be a percentage of the weapons damage (i guess between 50%/75% and 200%; definitely over 150% is possible). Because of that Weapon effects are probably way lesser effective on Hunter Weapons.
*Since I haven't got that many magazines with weapon effects, I cannot guess the upper limit. But if I have to guess I would say 100%.

The stock is an optional gun part that affects stability and handling of a weapon. Stocks have no additional properties.
It exists only in the two lowest tiers (grey: Stock I; green: Stock II). I refer only to the better Stock II (because I recycled all the other).

It adds 15% stability. [Note that the stability value has decimal places that are not shown. Thats why it seems to be not always exactly 15%.]
But it adds also 0.3 s to handling.

Thats why it is not necessary to have a stock if a weapon doesn't need stability or has already reached the cap at 100 stability.

The stock is an optional gun part that affects the stability. Sights have no additional properties.
It exists only in the two lowest tiers (grey: Sight I; green: Sight II). I refer only to the better Sight II (because I recycled all the other).

It adds 15% accuracy. [Note that the stability value has decimal places that are not shown. Thats why it seems to be not always exactly 15%.]

I don't know if it only affects your shots when aiming with the sight. At least it seems to be more accurate when aiming. But thats also the case with the revolver which has no special sight.

There are two different sights.
Since they are in the center when aiming I advice to test which one suits your barrel better (Though I always use the slim one).

The core is a gun part that is equipped in a special slot in the frame. Cores have no additional properties.
The main source of cores are magic chests (they drop only from higher tier chests).

There are three different core types:

• Flamethrower - "Flames the enemy with a burning mixture that deals 166%** dmg/s. 2* Special Ammo per sec."
  
• Ice Storm - Fires a hail of icy shards that deal 200% damage and penetrate enemies. 1* Special Ammo per shot.
  
• Annihilator - Fires an energy sphere that deals 316%** dmg/s to enemies within 400*** range when contacted. 5* special ammo per shot.

* Seems to be always this number.
** Due to limitet example size I cannot guess the upper limit.
*** I have no clue how to translate this into distance. I guess higher is better.

Since the damage is based on the guns damage the cores are probably less effective on hunter guns.

Also two of the guns stats are capped:

• Accuracy: 100
  
• Stability: 100

The most I got for the other stats :
Damage: 211 (will calculate it, when I studied all parts)
Fire Rate: 1000 (could be a cap, not sure)
Reload Speed: 1.1
Magazine Size: 42
Range: 28 (could maybe be better, because i have not every legendary barrel, i can calculate when i studied the barrels)
Handling: 0.2 (you have to use a max damaged grip for this)

I like using a high damage rifle with the grip property that armor explodes on being destroyed. This kills the normal soldiers most of the time with one hit. WIth this playstile I do not necessarily need a weapon effect on my magazine.

Since you have limited ammo in the arena take one of every weapon type with you (two are most of the time enough for me). By playing that way I never had to craft ammo containers. Also take some armor with you.

A shotgun combined with a cryo magazine is nice. The shotgun has many bullets so the chance of acivation is very high. Since there is a cryo explosion a whole part of the horde is frozen.

I only use higher tier parts, if the part is exactly what I want. For example I like Singleshot-Autofire Rifles with armor explosion. So if I only have purple grips with that I wont switch to legendary ones, since the better stats aren't worth it (handling for grips, range for barrels).