Again, you would be wrong. You need to read Heller again. It is far more complicated and nuanced than you suggest. Specifically, the 5-4 split was only about specific DC restrictions, not whether there was an individual right under the 2nd amendment. In other words, some of the 4 dissenters conceded the individual right, but simply argued that some of the specific restrictions were permissible.
there were follow up cases challenging other aspects of DC gun registration, etc. Some were upheld and some were struck down. It is clear from those and other decisions, however, that there is virtually no support for any suggestion that any kind of ammunition ban or serious restriction would survive under the 2nd Amendment or Heller.