Not bad.
Based on legal history I would change a few things.
I would make the explanatory clauses into separate sentences and include words to the effect that there may well be numerous unenumerated reasons.
The sentence protecting the right should do away with the word "right" since it has been read to imply that only an existing right was being protected without details about that right.
Instead, I would prohibit the federal or state governments from passing any law denying to unimprisoned and uninstitutionalized persons over the age of 14 the liberty to make, sell, buy, trade, keep, bear or use any type of weapons or items even weakly related to such items except where unjustified harm is done to others. No registration, licensing, or other mandates may infringe the liberty protected and no requirement shall exist to mark weapons for identification.
I would then add that the above does not include weapons which derive their destructive power from fission or fusion of atoms or self-replicating organisms.
I'm sure that anti-gunners will find flaws in this, but it would be better than what we have now.
Remember, we also have over 200 years of liberal mucking with history to shape our wording.