There's a degree of commotion about in which ways spore mines are allowed to voluntarily move. Basically, a lot of people are playing as if they were using the 4th edition codex.
Here's the entire Living Bomb section, which governs nearly all the special rules of spore mines except for deployment.
Codex Tyranids 5th Edition wrote:Living Bomb: Each Spore Mine model is treated as an individual unit. Spore Mines are always ignored for the purposes of any and all mission objectives. Spore Mines are not subject to Instinctive Behaviour, never go to ground (voluntarily or otherwise), run or fall back. At the beginning of the Tyranid Movement phase, each Spore Mine moves D6" in a direction determined by rolling the scatter dice (Tyranid player chooses the direction if a hit is rolled).
If a Spore Mine suffers a wound, touches an enemy model, impassable terrain, or it ends any Movement phase within 2" of an enemy unit, it immediately explodes. Place the central hole of the large blast marker over the Spore Mine and resolve any hits at a Strength of 4 and AP of 4. Spore Mines that drift off the table or into a friendly unit are immediately removed from play.
Common misconceptions about spore mines:
Spore mines cannot assault.
Incorrect. Despite being specific to disallow running and going to ground, no portion of the Living Bomb rules disallow assault. The assumption that they may not assault is a holdover from the 4th edition spore mine rules that specifically state "Spore Mines cannot make Assault moves." The idea of a heat-seaking bomb homing in on bodies or vehicles is too alarming for people to grasp, apparently.
Tank Shocked spore mines instantly detonate.
Incorrect. Close, though. See, although a tank shock will bring the models into contact, passing the Morale test acts "as if it was not there." Even so, you can overcome this by finishing your tank shock move within 2" of the spore mine and waiting for the movement phase to end.
Spore mines cannot hurt tanks due to the hole not being over the vehicle.
Incorrect. Spore mines don't resolve the large blast marker as an S4 AP4 large blast. They resolve any hits from the large blast as S4 AP4. In other words, there are no partials.
Spore mines may only drift during the Movement phase.
Arguable. At the beginning of the Movement phase, spore mines automatically "move" D6 inches in a direction. Since this IS a move, we can assume this movement is their entire movement for the phase. However, nothing in the Living Bomb section states that this particular movement replaces the entirety of their move. In other words, a spore mine that drifts 2 inches at the beginning of the movement phase is free to move 4 inches following the rules for regular Infantry models, so long as you do it after drifting and before moving another model. Spore mines are Infantry according to their army list entry, after all.
Spore mines provide Kill Points.
Incorrect. Who still argues this? I've read it posted on various boards, despite how moronic it is. Nothing could possibly be more clear than "any and all mission objectives."
Educate yourself. While I won't argue in favor of some of the sillier
RAW, like detonating spore mines that can survive their own detonation if they roll a 1, I will argue in favor of spore mines that actually hunt down enemies as allowed by the rules and portrayed in the fluff. Tyranids are a shooting gallery already, there's no need to make up fake rules that exaggerate this.
