I took the time to watch some videos of people testing this.
- A pneumatic roofing nailer couldn't stick a nail into the board from even 2-3cm away.
- A pneumatic framing nailer couldn't stick a nail into a pine board from 5m; the nails all tumbled badly past about 15cm.
- This guy then proceeded to weld a freakin' barrel, almost a meter long, onto his framing nailer in hopes of improving accuracy. While it did achieve that goal, he only got about 1cm of penetration from ~3m.
- A PA nailer with green blanks stuck a 1.5" nail into a railroad tie about an inch deep from 2m, and a 2.5" nail about 1cm deep from 3m.
- More interestingly, the above nailer only got about 5cm of penetration in a ballistic gel block with a 1.5" nail and a green blank from 15cm away. A yellow blank from the same distance got about 12cm of penetration.
Aside from all that, we're talking about a tool designed to push a fastener into material while in contact with said material. A gun is a tool designed to push a bullet into a target at a distance with some level of designed-in accuracy. These are not the same thing. A power nailer can certainly be used as a gun, but it can also be used as a step stool, a ruler, or a door stop. Usage outside intended purpose doesn't change the nature of an object.
Hey, if you want to call your PA nailer a nail gun, that's fine. There's no law requiring accuracy in speech, and of the entire power hammer category a PA nailer is probably closest.
I've always read "don't let your out or they will commit ethnic cleansing on your neighborhood fauna" as similar to "treat all firearms as if they are loaded". While it is obviously situational (some cats don't hunt/hunt well, obviously some guns aren't loaded), the consequences of getting it wrong are pretty bad.