Some friends asked the same question. Having bought War For Cybertron Megatron, and still need to tighten his arm rotation so that it doesn't flop from side to side when posing him. Who can show the detailed images of this arm fix ?
At your local drug store. It's called "Clear nail Polish". I had same problem and all you gotta do is let some flow in the joint, dry, then you'll have a tight WFC megatron arm.
I, personally, use Tamiya Model Cement for things like this. Rather than buying a bottle of clear nail polish. Pop the ball joint out, put a layer inside the socket, let it dry overnight, and then shove that ball joint back in. Should be tighter than it was previously.