The United States' citizens have the right to bear arms under the 2nd amendment. There is no amendment protecting your right to own ammunition or magazines for these firearms.
My suggestion is to allow the United States' citizens to keep their pistols, assault rifles, hunting rifles, etc. but limit their magazine possession to the following:
Allow possession of a small pistol magazine to any US citizen who is qualified to own a pistol
Allow large magazines of any weapon to be rented and used in certain premises such as firing ranges, hunting grounds, etc.