https://warframe.fandom.com/wiki/Atomos#:~:text=Punch%20Through%20will%20cause%20the,first%20target%2C%20and%20vice%20versa.

• "Punch Through will cause the main beam to chain independently from each additional target hit, potentially doubling or tripling the total damage output when fired into a crowd. The chain from the target hit after the Punch Through can deal damage to the first target, and vice versa."
• The electric Tesla Chains can hit headshots by themselves, so go for Primary Deadhead instead of Primary Merciless, as Deadhead has a longer duration.