I worked for a public shooting range for a while and saw some incredible stuff, Man walks in and says do you have some .44 magnum, we discuss the options, and he purchases some and go's out onto the range, He comes back 30 minutes later and asks if we have some .41 magnum ammo, Yes sir, we do, what bullet weight and style do you want? Then he comes back and says, these .41 Cartridges aren't working too well, only half are going bang, We talk for a minute and I ask if he has any of the fired rounds, yes, he says, and presents them to me. The fired cases were disfigured, off center bulging, He was firing .41 mags in a .44, sometimes the primer did line up, and went bang. His enterpretation, was .44 mag, loudenboomer, .41 less loudenboomer, and probably would have tried .357 next and wondered why the cartridges fell out the end of the cylinder.
I cannot tell you how many people, would come to the shooting line, plunk down their gear and then start heading downrange to put up targets, while the firing line was hot and firing. We would call them back on the loudspeaker while calling an immediate ceasefire, explain the problem and ask them if they would like to wear a target on their back as they went downrange again.
Man brings in a scope to our local gunshop, wants to have it sighted in.

I'm not kidding.
I'm just a shooter at the public range, and this young man first go's down range while every body is firing on the pistol line, We catch him quick and bring him back and explain wait for the cease fire, then after he starts firing, he has a .25acp cheap, like Raven, pistol, as he is firing I hear the pistol going full auto, during the cease fire, he asks me, " this gun works great on automatic, how do I get it to fire one shot at a time." of course I advised him correctly to send the firearm back, and this was not only incorrect, but could get him in trouble.