The current estimates are 250-300 million guns in the hands of 80-85 million gun owners.
Murder rates are running 12,000-15,000 annually these days, about 70% of which are firearm homicides, so 8500-10,500.
Now, if you include accidental, justifiable and suicide, the number of firearm deaths more than triples to around 32,000-35,000 annually. The extreme majority of that increase is suicide; 20,000-22,000. Accidental firearm deaths vary more than the other numbers, but have usually been fewer than 1,000 annually.
So, if we drop suicides and justifiable homicides (very negligible number), assume 10,000 firearm homicides (higher than current average) as well as a relatively high 1,000 accidental deaths, and go with the lower estimates on gun owners and guns, that'd be 11,000 murder and accident firearm deaths for 80 million gun owners with 200 million guns, or .0138% of gun owners and .0044% of guns. This, of course, also assumes one victim per gun and gun owner. We know that's oversimplified in the extreme. We also know that legal gun owners account for a minuscule percentage of gun crime. The reality is that, when talking legal gun owners, we need to move the decimal a couple more spots to the left.