with both barrels
With extreme force or vigor. The phrase refers to the barrels of a gun. You have to know that she's going to come at us with both barrels if we fire her, so just be prepared. The team looked a bit lackluster in their first game, but they've come out with both barrels tonight.
both barrels, with
With full force, as in When I scolded her for stealing, I let her have it with both barrels. This term alludes to firing with both barrels of a double-barreled shotgun. [Colloquial; mid-1900s]
with both barrels
with unrestrained force or emotion. informal The barrels in question are the two barrels of a firearm.