This is highly detailed Rapier cannon, it is armed with Laser Destroyer Array

A bulky, armoured track unit (Horus Heresy Era Wargear), which mounts a powerful antomantic reactor, the Rapier is often armed with a powerful quad lascannon known as a laser destroyer

You can download it here: https://cults3d.com/en/3d-model/game/rapier-laser-destroyer-array-cannon