It's unfortunate that people who can't conduct themselves responsibly make this a topic, but just because 15-25% of people like yourself can behave responsibly around firearms doesn't necessarily mean they should be available to 100% of people if those people can't prove beforehand that they should be allowed to possess them.
Do you have a source to back the bolded statement up? Because, if 75-85% of people
couldn't behave responsibly around guns, we should expect to see a higher incident percentage of accidents and intentional violent actions involving guns.
Roughly 1/3 of adults in the United States owns a gun, according to a stat in a Mother Jones article. According to the Gun Violence Archive, there were 50,000 incidents of gun violence in 2015. Let's throw the 20,000 suicides in there as well. So, 70,000 incidents of gun violence, self-inflicted or otherwise.
So, what does that mean, percentage-wise?
240,000,000 estimated adults (Census Estimate 2013). If 33% of those own guns, that's 80,000,000 gun owners.
Now, 70,000 annual gun incidents. That would mean that in a given year, 0.0875% of gun owners act irresponsibly (70,000 divided by 80,000,000), resulting in either intentional or accidental harm to themselves or others. And, that assumes only one unique gun owner and one unique victim for each incident.
Even if we multiply that number by 70 to account for a lifetime of years of being able to handle guns, the incident rate is only pulling in (EDIT) 6.125% of gun owners. Now, it might just be me, but less than 7% isn't exactly comparable to the 75-85% "estimate" you're throwing out.
Of course, that doesn't include irresponsible handling that doesn't result in an accidental injury/death, such as not putting the safety on while walking with a rifle out to the shooting range where the trigger
isn't accidentally pulled. But, you're never going to have a reliable stat on that.