just throw it into your bit's box, and once you need you have one.

It's basically there to fill that last hole in the base. I'm sure they could have made a spare ammo/power pack to do that job to be more thematic, but what do you do with a storage-world full of tactical rocks? 

35 minutes ago, Domhnall said:

It's basically there to fill that last hole in the base. I'm sure they could have made a spare ammo/power pack to do that job to be more thematic, but what do you do with a storage-world full of tactical rocks? 

You misspelled Ammo Grot....

GW should give us rules to throw tactical rocks if a model comes with a molded tactical rock. Range "Str of model" x2 Ballistic Skill 2+, Str 17, AP -6, DMG "All your wounds". One use but allowed rerolls for hits, wounds, and ignores all special rules target may have included invul saves.