Given my personal experience, I'd say criminality is way more linked to the cultural and social context than widespread gun ownership.
In this regard
my country would be a prime example, with
extremely high gun ownership (virtually every male Swiss citizen is
given a military grade weapon by his 20's, and sometimes even as early as 16), but also low crime and
murder rates (I would even rate Switzerland much lower on the scale, as statistics are most likely inflated by the
Euthanasia tourism).
More so, in Switzerland, the gun and
militia culture makes it that gun ownership is much more widespread over the whole population (25-30% would be a minimum estimate, as virtually all male adult citizen are concerned).
Yet legally held guns involved in murders are confined to suicides and family dramas.