I've got the same problem as Daniel336Cobra in this thread
I've got an Item (a gun) with a capability storing a list of ItemStacks (attachments - scopes, circuits, etc.). My circuit in that capability is an ItemStack that has another (different) capability that controls how often the gun should fire. Every time the gun is shot (in onUsingTick) a counter in my circuit's capability is incremented. This counter is reset in onPlayerStoppedUsing. Both capabilities are stored in the Gun'