Collider on Bone changes Bone Origin/Pivot

I am making a very simple tank vehicle and have rigged it up in Cinema 4D R14.042 with 3 bones.

I have added it to my unity project and everything imports correctly. Since the colliders need to move when the turret and barrel move, I have attached a box collider to the body, turret, and barrel bone. This in turn changes the origin of movement for my turret so when I rotate it it does not correctly rotate about the turret middle (see image)

How do I get colliders that move with the bones/mesh but also maintain there original origins so that programmatic animation is correct?

Edit: The selected answer was the solution but I have just come across this great video on creating custom pivots and thought I would share: http://cgcookie.com/unity/2013/05/14/creating-custom-pivots-in-unity/