On robotic snipers, you can find Sentinel firing cores in
arc raiders trading
Sentinels, in Arc Raiders, are extremely rare enemies. They're sniper-turrets placed on buildings that aim at nearby players and then deal massive damage. Sentinels can be found in small numbers, but they are a good source of Sentinel Firing Cores. This item is needed to upgrade the Gunsmith table. Below I will explain where you can find Sentinels in different maps as well as an alternate way to find Firing cores.
Sentinels are rare and spawn randomly, but they will always appear on high ground with long views so they can shoot at people from distance. Night Raids seems to have a greater spawning rate. I've personally observed them in the following places:
The Breach, Dam Battlegrounds
Buried City Town Hall
Spaceport: Departure Hall
The Blue Gate - Pilgrim's peak
If a Sentinel comes near, you will see the laser sweep the area. When a Sentinel sees you, it will focus the laser on you and give you time to move behind cover. Cover will help you close the distance and get in range of the Sentinel. As they don't have much health, you'll need less effort to kill them if it's possible to get close.
Sentinels carry Sentinel Fire Cores. They are usually found at the rate of one per Sentinel. Arc Couriers are the white saucer shaped objects you can break open. These are usually marked by smoke plumes. It is worth opening every courier, but keep in mind that the number of crashed Couriers increases during Electromagnetic Squalls.
Il Toro: Uncommon, Shotgun, Shotgun Ammo
Il Toro has a lot of power, but its range and fire rate are not up to par. It's best in maps with tight spaces like Stella Montis. In Spaceport or Dam Battlegrounds however, its power is only felt when you get inside buildings. There are other options that can be deadly in close quarters. Even so, ambushing someone with an Il Toro is a great way to guarantee your victory.
Arpeggio: Uncommon, Assault Rifle, Medium Ammo
Meh? Arpeggio uses bursts of fire to deliver average damage within a reasonable range. If you want to use this gun inside, it's not worth the effort. You should get attachments which focus its fire for longer ranges. Arpeggio lacks a lot of power, particularly in PvE.
Venator: Rare, Pistol, Medium Ammo
The gun used to be the most powerful in the game. Patches have changed that. The pinpoint control is useful for fighting against other Raiders and also lighter Arcs. Keep in mind, however, that this pistol is incredibly loud and consumes more ammunition than other guns.
Torrente: Rare, LMG, Medium Ammo
This LMG handheld is designed for PvE. It can reduce Arc robots into shrapnel. However, it's inaccurate and slow, making it difficult to get the edge over players. You can cause a lot of damage if you are able to get an early advantage.
Vulcano: Epic, Shotgun, Shotgun Ammo
Shotguns have a hard time finding their niche. The Vulcano costs more than the Il Toro but is only marginally better. It's a bad shotgun, with poor range, poor fire rate and no armor-breaking ability. But in small player matches, you can still do serious damage.
Bobcat Epic: SMG Light Ammo
The Bobcat has a lot of kick, so you'll want to add attachments that reduce recoil for controlled fire. The Bobcat has a kick. Make sure you add accessories that will reduce recoil to achieve controlled fire.
Bettina - Epic Assault Rifle with Heavy Ammo
This AR is faster and more powerful than others, suited for PvE combat against Arc’s heavier minions. Heavy Ammo is required to run it, so be sure to bring plenty.
Jupiter: Epic Sniper Rifle & Energy Clips
The best Sniper Rifle is built with a Queen Reactor, so it could be better. The weapon works well in PvE to disassemble Arc enemies from a distance, using powerful armor-breaking shots. But it is too slow and awkward for spry players. If you want to go hunting Rocketeers or Bastions but not people, then this is what you need.
Rattler: Common, Assault Rifle, Medium Ammo
Rattlers are cheap and hardly worth their price. They lack punch and feel ill-suited to all combat except for the basic Hornets or Wasps. Although it does have decent armor penetration, the Rattler is an early-game weapon to be traded for something more powerful.
Osprey: Rare, Sniper Rifle, Medium Ammo
Although long range combat sounds great, the Osprey doesn't have the power or accuracy to be a good fit for most players. It's hard to kill Arc opponents with its average armor penetrating, and players tend to avoid being killed until they find cover. You can use it to protect allies in the air or to weaken enemy forces from stealth.
Hullcracker - Epic, Special Launcher Ammo
This weapon, which was once a powerful one, has been weakened by patches. This grenade launcher can still be effective against enemies like Arc Raiders Bastions. But it is inaccurate and terrible when used by other players. You'll also struggle to hit flying opponents like the Rocketeers.
Hairpin: Common, Pistol, Light Ammo
The description even says that it is "tricky in battle", which is not something anyone wants from a weapon. This pistol has a built in silencer, but it's too weak to be of any real use. It would work better with anything else. Even if it's on, you should use it to its intended purpose - to sneak attack and to make headshots - before switching to an actual gun for combat.
These weapons were designed to be used against other Arc Raiders players - but we wouldn't suggest doing anything so terrible.
Kettle
Anvil
Stitcher
They can be quickly drawn to slash opponents and deal quick damage, even without armor penetration. This is especially useful in close-quarters battles when players are able to see one another.
Sentinels can be found in Arc Raiders
