A little example of what I am trying to do
Let me go further in depth.
I'm creating an FPS. The gun and arms are welded to the head. Inside the gun there is a part called main. I want to rotate the joint so that the gun is rotated in such a way that the main is always pointing to the camera's lookVector. I'm hoping the screenshot I showed above will help explain this in more detail.
I thought that I would need to use toObjectSpace() but my attempt with this was a bit wacky.
I tried CF = Joint.C1:toObjectSpace(CFrame.new(Equipped.Main.CFrame.p, workspace.CurrentCamera.CFrame.lookVector))
My lack of understanding when it comes to some of the CFrame operators + the lack of documentation on ROBLOX's part when it comes to these operators is probably to blame here.

4 comments
@BlueTaslem Mind checking this out?
One, you never even explained what the joint is. Two, you can't "point at a lookVector". You can point at a position, which a vector is not. Do you mean to point at thiss: camera.CFrame.p + camera.Cframe.lookVector ?
Vector: A quantity having direction as well as magnitude, especially as determining the position of one point in space relative to another.
@Cabbler, Next time you comment here (in a rather stern tone), please make sure you know what you're talking about.