It seems like those who are poo-pooing the picture as not a big deal at all must not be seeing the same thing I am. I'm envisioning a not-very-careful person messing around with a loaded gun taking pictures down the barrel. Who knows how many images he took? Who knows what kind of gun handling he was using during the photo session? All you're looking at is a static image of a bullet in a barrel. What I'm seeing is the whole session, and I wouldn't want to be there during that particular "photo op".
Who here would seriously take a loaded pistol out of a holster/safe/whatever and start taking pictures of it before checking, and double checking, that it wasn't loaded? Do you also do other things with it loaded?
No matter how trivial some think it is, I still say it's stupid and completely irresponsible handling of a loaded gun.