Yet you seem to admit that the very "pre-existing" right to which we are referring, is the right that shall not be infringed in the Second Amendment. The Second Amendment doesn't create a right. If it doesn't create a right, then how do you justify suggesting that it only protects a part of the right to which it refers?
There is an individual RKBA. That right is protected by each state from state infringement.
The second amendment protects the RKBA as part of a Militia. That right is protected from federal infringement.