The "common use" definition is a little messy.
My first problem with it is that automatics are not in common use only because they have been heavily restricted or banned since 1935.
But they are in common use for the same uses that would be protected under the second amendment. Every military and police organization in the world keeps automatic rifles and submachine guns, so the general militia should have access to them.
As far as semiautomatics are concerned, I don't see how you could argue that they are not in common use.
You're right, there is a bit of circular logic in defining fully automatic firearms as bannable because they are not in common use when the reason they are not in common use is because they are banned.
However, it is quite clear that if a firearm IS in common use, and ARs and the like certainly are, then it is protected by the Second Amendment.
I don't see NY, CO or CA's AWB standing up in SCOTUS.