Flechette Blasters are a type of weapon used by Adeptus Mechanicus Skitarii. A very interesting weapon, it occupies its own unique little page as it is a specialised form of Galvanic Weapon. A lightweight but lethal firearm, it is the favoured tool of Sicarian Infiltrators. This silenced weapon fires hundreds of tiny darts, each of which bears a dormant cell awakened in the gun's chamber. Where one dart hits, it emits a homing beacon that attracts others, resulting in a series of impacts that burrow through bone.
Think of it like freezing water in a crack to break something bit by bit. The darts smash into the opening made or started by the first one, wedging more and more darts in to break open the target and the whole mess presses ever deeper.
In terms of tabletop, these nasty little pistols are available on the Infiltrators paired with a Taser Goad. It's got rather low strength at S3, but 5 (FIVE!) shots means it packs almost as much punch as a rapid-firing bolter, while being fireable in melee. Overall, it is a rather meh weapon that obviously suffers against enemy with decent armour. So stay clear from MEQs and above.