Joints are never supposed to be connected for vehicles.
Strato may have done this unknowingly, or he may have done it to make sure nobody incompetent could steal his stuff.
Also, your other topic is locked, even though you bumped it to ask for help with joints.
The most likely thing to name the barrel is indeed muzzlePoint. I do not know for sure, but it is a 90% sure thing. Try it, and if it doesn't work, try barrel.
The numbers after the name of the joint don't matter, but you should attach an "100" to the end of all of your groups, for the bot turret. Adding a number to the end of joint names makes problems, I'm pretty sure.