I noticed the other guide isn’t 100% accurate because it’s now out of date, reason below ⬇️
Disclaimer: There are now 13 weapons in total to obtain. It used to be 12, but with the addition of the Golden Loop Update, the HALPS laser beam rifle is a new addition of that and is included into the base game of the Xbox port, because it launched with the game on Xbox. Meaning there is now 8 Basic weapons and 5 Special weapons.
Also, ANY weapon obtained through means which don’t include actual gameplay effort, such as the Rapiér obtained from the Game Pass Ultimate Perk “Dressed to Kill Bundle” or any weapons from signing up for the Arkane newsletters, does NOT count towards the achievement. Please infuse weapons through normal means and make sure they’re either default or blue tier ONLY. Location for a standard weapons can be found below in the guide.
Here is my version of the guide:
You need 8 BASIC weapons, ideally the lowest tier or the blue/aqua tiered ones (Common and Uncommon). The purple tiers (Epic tier) do not seem to count towards the achievement. I believe this is because they come with special attachments and it somehow voids it as the game must assume it’s a unique weapon. You DO NOT need to infuse every single tier of a gun, just pick either grey or blue tier and infuse it.
All 8 BASIC and UNCOMMON weapons can be found in the LIBRARY in UPDAAM during the MORNING. The library is on the way to Colt’s home and pretty much the center of the entire map.
There will be 5 enemies inside the Library to eliminate too, then you can go ahead and grab the following:
— PT-6 ‘SPIKER’ (Nail Gun)
— Tribunàl (Pistol)
— LIMP-10 (Machine Pistol)
— The Fourpounder (Magnum Pistol)
— Vopat Trencher (Pump Shotgun)
— Strelak 50-50 (Drum Mag Shotgun)
— Rapiér (Hunting Rifle)
— MG-1 ‘PEPPER MILL’ (Machine Gun)
***Friendly reminder that you can only grab 3 at a time, due to the character only being able to hold 3 weapons at once.
All 8 of these will be scattered on the ground and upper floors of the Library. Collect RESIDUUM whilst you’re there and TRINKETS to sacrifice those later for more RESIDUUM.
The remaining 5 will be SPECIAL weapons, they will require others means in order to acquire those:
— Constancy Automatic (Machine Pistol): Acquired by killing FRANK SPICER, he is in FRISTAD ROCK during the MORNING. This is a Visionary so he will be a story progression enemy, you can get the gun off him as a drop when you eliminate him.
— Sepulchra Breteira (Sniper Rifle): Can be obtained in two ways.
1) Defeat the invading Julianna and she will drop it. But note: She will not have it until about halfway into the game.
2) In UPDAAM, during the AFTERNOON. An eternalist will speak on the mic saying they left a gift for you on the path to Dorsey Manor (behind Colt’s home). In the surrounding buildings and rooftops, there will be multiple Snipers ready to assault you when you get to the present. I always collected mine in the building opposite Otto’s Workshop.
***I believe this is a scripted, one-off event because it’s always only triggered for me around the halfway point of the game (on PS5 and Xbox). But after that point the sniper should always be in the general area.
— Strelak Verso (Akimbo automatic pistols): Can be acquired in the ordnance depot in the COMPLEX, during NOON. You can follow an ARSENAL LEAD for it to mark where to go.
As for the battery puzzle itself:
You need 4 batteries; 1 of which is already in the deposit so technically just 3. Run out to the LOOP CONTROL ROOM (you’ve been there very early in the game) and there should be 3 batteries scattered around that room: 1 in the projector, 2 on the floor. Charge all 3 in the battery charging station and run to the ordnance depot door to deposit them.
— Heritage Gun (Transformative Shotgun): Can be acquired by completing Charlie’s Game in KARL’S BAY, during the EVENING. Please refer to VG247’s (gaming website) text and/or video guide of this quest line as it’s fairly lengthly
***This weapon also counts towards 1 of 5 of the games needed for “A Charlie Montague Game” Achievement.
And LASTLY, the newest weapon:
— HALPS PROTOTYPE (Laser Beam Rifle): This can be acquired in the COMPLEX, during the MORNING. Simply head to Wenjie’s Lab out by the far end of the map and look for a green and white building to the left of the main tower of the lab. When you get inside, you’ll see a small room with two sensors inside, just run in and pull the two levers under the HALPS Prototype and run out immediately. The sensors will immediately detect you and the laser from the weapon will deflect to the sensors to kill you. Run in again and collect the weapon. And remember to collect enough RESIDUUM to infuse it.