Jake Paul has moved on from punching bags -- the Problem Child just used a Soundcloud rapper to hone his boxing skills ... hitting Lil Pump with a vicious body shot!!
The internet star and fighter welcomed the "Gucci Gang" musician on his "BS with Jake Paul" podcast this week ... and about halfway through the episode, Pump asked if Paul was willing to punch him in the stomach as hard as he could -- just so he could experience what it feels like.
Pump was fully committed to the stunt .