maybe he stacked reload speed? are there any reload speed augments for Benedict? I know gear wise he is either using his character legendary or the veil breaker rounds for a +20%ish reload buff. The other gear was either the shard of jennar (ambra char legendary) or the bola’s target finder, which does not increase reload speed. he could also be stacking attack speed to get that fourth rocket on. i know the bola’s target finder has a secondary stat of attack speed.
I’m not 100% sure on how the rocket picks its tracking target, but previous posts have lead me to believe that it’s the last person hit that gets tracked.