It's been awhile since I had 4.4 if at all but to get a barrel it's best to try fighting Barrel master to get one though maybe any enemy can drop it. Barrel master is located near the exit to the town there is a large group of barrels and one is very big compared to the others if you loot that one Barrel master will immediately attack you I'd advise training up till you feel you can beat him the Giant rat you get as a companion can help or you can fight him to get exp best you take his weapon away first. Any case getting the barrel weapon is rng so you'll have to keep trying till it drops.