Happens 500k to 3 million times a year.
"Studies" that claim this are just surveys that end up with wrong data after extrapolating - the fact that has been pointed out plenty of times. Here are some reasons:
1. Surveys work when you look for something that happens a lot. When instead you look for small number of cases, small errors result in large errors when you extrapolate. Say you are looking for something that really happens 1% of the time. You ask 100 people. If out of 99 cases where it DID NOT happen a single person says it did, you just doubled the true number. The mistake in opposite direction is much less likely since that 1 person which HAD this happen would have not reported it.
2. In this specific case, gun owners responding to these surveys would be more prone to claim a defensive gun use, either on purpose or not. This IS the main justification for many people for why they have a gun. So, many people want to instinctively think they've used the gun for self-defense when they may not have. Claims for self-defense could be along the lines of
- 'Someone had a threatening argument with me; I showed him that I was packing and he left me alone. Check.'
- 'I had a fender bender and the other driver was really angry with me. Just in case, I made sure he knows I have a gun. Check.'
- 'I am a woman going to the store and a guy looked suspicious by the entrance. I made sure he saw my gun, so I felt safer. Check.'
- 'I took a gun when going to bad part of town. Check.'
3. Whether use of gun in self defense is benefiting or not is unclear. It's hard to survey DEAD people who tried to use their gun in self defense and died AS A RESULT. It's also hard to survey DEAD people who simply had a gun for self defense but it got used against them (and then stolen of course).
There are a lot more reasons and lots of text has been written on this but pro-gunners just like to stick with this fantasy that 1 out of every 32 gun owners is using a gun in self defense
each and every year.