The unique affix makes Hungering Arrow always pierce the first 4 targets hit, and it never pierces more than 4 times. The Puncturing Arrow rune has no effect. Buriza-Do Kyanon also has no effect; the limit of 4 does not increase. The arrow cannot retarget to an enemy more than 70 yards away, but it can bounce back and pierce the same target several times in a row. If the arrow hits a solid obstacle or if the demon hunter moves too far away from it, it disappears.
As of patch 2.6.9, it also increases Hungering Arrow damage.
Stats (Level 70)
The Ninth Cirri Satchel
"This satchel is cleverly designed so that the heads of arrows placed within fit into slots that serve as whetstones, sharpening the edges whenever an arrow is inserted or removed. Cirri's artistry remained unrecognized in his lifetime, so that only this quiver, numbered nine on the interior, survived to the present." —The Craft of War by Diadra the Scholar
Until the patch 2.7.0, the amount of pierces done by a single Arrow was theoretically unlimited. However, this proved to cause performance problems and block the Gears of Dreadlands set from reliably triggering its effects, and was changed to a hard cap of 4 pierces per shot.