We're told the bust went down Monday ... LAPD and the feds attempted to pull over a vehicle NBA YoungBoy was in because he has an outstanding federal warrant. That set off a short pursuit -- but once the car stopped, cops say the rapper bolted on foot.
Our law enforcement sources tell us the cops set up a perimeter and brought in a K-9 to help find YoungBoy. BTW, we're told the police dog didn't bite him -- but did sniff him out.
We're told the cops found a firearm in the vehicle -- unclear if that belongs to YoungBoy, but we know the feds have him now.