EDIT 12/9/2023 Bot Bootcamp has been removed once again.
EDIT 12/25/22 Mixed reports that this may no longer work in Bot Bootcamp even though the mode has returned. This may now need to be completed in live team modes, but some say it is still working in BB. 
EDIT 11/22/22 - Bot Bootcamp has returned.EDIT 11/08/22 - Bot Bootcamp was removed in the Winter 2022 update. According to the devs it seems like this may have been removed due to AI problems. It may be returning in a later update.
For now this achievement will need to be completed in regular matchmaking.(Currently can be completed against bots in Bot Bootcamp. Easiest method for me was on Aquarius right at the start of the match. Go grab the rifle and all four bots should be grouped together. Let your teammates dmg them a bit and fire away at the full health ones.)
Weapon spawn points in this game may seem really random, but each particular weapon pickup location only has 2 available weapons that will spawn at it (except Handgun spawns which have 3).
At each of the spots I list below you will either find a Shock Rifle or a Stalker Rifle. If the Stalker spawns then you won't be able to find the Shock that whole game in that weapon spawn. Try another spawn point (if there is one in that map) or quit out/wait for another match and try again.If you look just to the right of your minimap in game it will tell you where you are in the level. The capitilized locations I've notated below are actual spots in the map, so keep looking around (or marking spots using
until you find the spot I mention.
Locations:
Streets: on the Subway Balcony
Aquarius: in Hydro, down & left from the starting Blue Base, down/right from Yellow Base.
Launch Site: up in the Bunker Nest (left part of the Bunker that's the starting point for the capture team)
Fragmentation: at either starting base, Cliff Base or Canyon Base, on the left side near the launch/jump pad.
Highpower: 1st/2nd spawn behind either starting base at the landing pad. 3rd spawn is mid-left from Waterfall Base / mid-right from Tower Base, you'll find Overlook. Two weapon pickups are there - Ravager/Hydra and Stalker/Shock Rifle. There's a 4th spawn at Cave Pit (forward and left of Waterfall Base).
Deadlock: left rear of both Low Base and High Base spawns.
In order to get a "Chain Reaction", secondary chained damage to a nearby enemy must kill them.
There are 3 known methods of getting this achievement to pop:
1)
Fire the rifle at an enemy, then any other nearby enemies (within around 1-2 meters) will be shocked for a lesser amount of damage. That secondary dmg needs to kill the 2nd enemy.2)
Throw a gun on the ground and shoot it to cause chain damage to nearby enemies.3)
Shoot a vehicle (not the enemy) and the damage will harm the enemies in it, eventually killing them. A full warthog or tank works great! (This doesn't seem to always work if there aren't at least 2 people riding the vehicle) Tips for enemy-2-enemy chains:
- Shoot one of the enemies a couple times and then focus your fire on the other guy so the chain damage kills the one who's already weak.
- Wait for a teammate to damage one of them and then shoot the other guy if you're worried about running out of ammo before the chain kills him.