This can be obtained on Casual difficulty.
A perk that would be helpful would be Timeslip but its not needed
First step is to turn on power and activate pack a punch. After that you can begin getting all the pieces for the ray guns
Ray Gun Frames:There are 4 televisions around the map which must be activated and charged through kills.
The 4 locations are as follows:
-Site Entrance part of map near spawn. TV is located behind yellow fence near the tent
-Yellow House Backyard, TV is located on a table underneath the stairs going to the second floor
-Diner, TV is located directly across from the perk machine
-APD Control, TV is located on a table on one of the 4 corners of the pyramid
The TV's must be activated in a specific order. To figure out this order, visit each TV until you find the one that's screen is lit up blue. Once you do, hold interact button and the tv should show the ray gun mark II on the screen.
Get a few kills around the tv until a number is shown on the screen. Remember this number then go to the next tv and repeat the process until you receive the number from all 4 TVs. Once you have all 4 numbers go to the computer in Operations and input the code from the TVs in the order you got them.
Behind you in Operations the frames for the ray guns will come up from a box.
If you're having trouble with the steps or prefer a video guide, here is a video from Glitch:
Ray Gun Assembly:There are 3 parts to the assembly around the map you must find. Each part has 3 locations
Tubing- On the dining table of Yellow House Downstairs, on a shelf of the Yellow House Upstairs, on a end table in the bedroom of Yellow House Upstairs
2nd Part- On a barrel to the left as soon as you enter Storage from Generators, on a shelf in Storage next to canned food, On one of the barrels next to the shelves in Storage
3rd Part- In Solitary its on the desk right before you enter APD Control, On a chair to the right as soon you enter APD Control from Solitary, On a tray table next to the command computers in APD Control
Once you have all the part go upstairs of Operations and use the crafting table to build the assembly kit there
If you're having trouble with the steps or prefer a video guide, here is a video from Glitch:
Crafting the Guns:Now with everything built we start on each element.
Step 1: Double Pack a Punch a weapon to get an elemental perk on any weapon, depending on which element you get determines which ray gun you upgrade. If you don't get the element you want or are working on a second one then you can repack your weapon at the pack a punch machine to get a new element on your weapon
Ray Gun Mark II-X (Cryofreeze)- Once you obtain Cryofreeze on one of your upgraded weapons, you must find a filing cabinet drawer that has a blue gas coming from it.
The 3 locations for it are:
-APD Interrogation, one of the drawers on the desk in the corner
-Operations, one of the filing cabinets in the garage of Operations
-Prisoner Holding, one of the filing cabinets next the door going back to spawn
Once you find the glowing cabinet, shoot the drawer with the cryofreeze weapon and it should open showing a canister. After you pick up the canister, head down to the bunker and zombies should spawn with blue gas coming off of them down there, shoot them with the cryofreeze weapon until they freeze and then knife them. They should drop a blue goo when they die that you can pick up. Repeat that process until you picked up 3 of the blue goo's.
After you finished that step, head to APD Control and hold the interact button on the empty cryo tube on a shelf next to the command computers. A circle should spawn and you need to get kills inside that circle until it disappears. When it does, pick up the cannister again
Once you have the cannister, grab a frame from the box in Operations and head upstairs to craft the ray gun.
Ray Gun Mark II-V (Kill O Watt) - Once you obtain Kill O Watt on one of your upgraded weapons, you must head to generators and find a panel sparking with electricity on one of the machines down there. Shoot the panel with your upgraded weapon and the panel will fall off exposing the cannister for you to pick up.
The second step is on the top part of the map there will be 5 power lines poles around the map. One of the 5 will be sparking yellow at the top of it, find the one that is sparking and shoot the top of it with your upgraded weapon until a yellow orb spawns at the top of it. Repeat the process until all 5 poles have the yellow orb and connect with lightning to each other.
Once they are all connected head towards the yellow house and right before the entrance there is a generator to the right, interact with it and the cannister will be placed and a circle will form at your feet. Kill zombies while standing in the circle until the circle disappears then you can pick the cannister back up.
Once you have the cannister, grab a frame from the box in Operations and head upstairs to craft the ray gun.
The Ray Gun Mark II-Y (Brain Rot) one requires the teleporter to be built. If you don't know how to build that then here is a video guide for that. Otherwise ignore this part:Ray Gun Mark II-Y (Brain Rot) - Once you obtain Brain Rot on one of your upgraded weapons, you must find a dirt pile on the top half of the map with green gas coming off of it.
The locations for the dirt pile are:
-Center Street, next to a light pole on the right side of the path leading from spawn.
-Green House Backyard, across from the mystery box location next to the green shed.
-Yellow House Backyard, to the right as soon as you enter the backyard from the house
Once you find the pile, turn a zombie with brain rot next to the pile and it will uncover the cannister for you to pick up.
When you pick it up, you will need to run around the map check each of the teleporter location for a glowing yellow orb floating on top of the teleporter pads. When you find it, place one of your teleporter pads in the spot and then shoot the orb until it goes down inside the teleporter.
Go around the map again until you find it a second time and repeat the process. When you shoot it a second time take the teleporter you just placed and the orb will be waiting for you once you teleport. You will know you did it right if you see a ball of fire in the bottom right of the screen when you're teleporting.
The orb will fly off to Storage where you must go and interact with the orb to place the cannister and a circle should spawn on the floor. Kill zombies while standing in the circle until the circle disappears then pick up the cannister.
Once you have the cannister, grab a frame from the box in Operations and head upstairs to craft the ray gun.
Ray Gun Mark II-Z (Fire Bomb) - Once you obtain Fire Bomb on one of your upgraded weapons, you must find a glowing red cabinet and shoot it to find the cannister for you to pick up.
The locations for the cabinet are:
-Yellow House Downstairs, inside the kitchen to the right of the door leading to the backyard
-Green House Downstairs, inside the kitchen on the left side next to the window
-Lounge, next to the pool table
Once you pick up the cannister head back to the top of the map and one of the houses will have a purple smoke coming out of the chimney. You must throw a grenade into the top of the chimney until the smoke stops.
When the smoke stops head into the house that had the smoke coming from it and interact with the fireplace to place your canister and spawn a circle on the ground. Kill zombies while standing in the circle until it disappears then interact with the fireplace again to pick the canister back up.
Once you have the cannister, grab a frame from the box in Operations and head upstairs to craft the ray gun.
If you prefer a video guide, this is a good short one from Glitch with timestamps for each element: