Just because I didnt know this, imma post it here, found it on wiki.
Apparently this ability has sort of upgrades as you lvl. At 30 it will shoot a maximum of 4 pieces of ammo, you CAN miss completely. At 50 it can shoot as many as 5 and at 75 it is possible to shoot 6. The rng AF1+1 hands "Enhance Barrage" by adding an additional shot, making it possible to shoot 7 pieces of ammo at once! You gain TP proportionate to the number of shots connecting, so if you gain 14% per shot and land all 6 at 75 you would instantly have 84%tp.
Also, it isn't as painful when you miss barrage as some ppl think. Barrage calculates each shot, and if a shot misses it automatically terminates there without firing any more shots. This means if your first shot misses you will miss barrage completely but you will only lose 1 arrow/bolt/bullet. While this is nice for conserving ammo, it means that barrage is instantly killed by blink. A shadow absorbing your first shot will kill the effect entierly without stripping all shadows, as one might expect.