via The Black Library
Bloodspire follows the righteous sons of Sanguinius as they lay siege to an impregnable fortress. It’s a kind of the-unstoppable-force-meets-the-immovable-object sort of deal, except that this force has a jump pack and a chainsword and the object is a bastion bristling with autocannons and missile silos.
The story features a hero that will be familiar to Blood Angel fans: Brother Tycho. Tycho is destined to fall with glory as a captain on the battlefields of Armageddon, but this audio drama shows a younger incarnation of him, a sergeant of the Third Company leading his squad into the teeth of the enemy's fire.
link to purchase the audio drama
http://www.blacklibrary.com/warhammer-40000/Space-Marine-Battles/bloodspire-mp3.html