The stubby one on the left is a 40 S&W case. It's bulged out of shape, and split, because someone fired it in a 45 ACP chamber. Ouch!
The middle cartridge case is headstamped as being a .303 Savage round. But the case is deformed into the correct shape for .303 British chamber (minus the neck). No, a .303 Savage is not the same as a .303 British.
And lastly, the right hand case is headstamped as a .300 Win. Mag. We know that cartridge has a short neck, but it's not that short. In this case, it's apparent the shooter fired the .300 Win. Mag. in a much longer .300 Wthby. Mag. chamber.
From the appearance of the cases, I suspect the guns and shooters all survived these episodes. And since I only found one example of each, I'm hopeful the shooters noticed their error after the first shot. However, it's not hard to imagine a catastrophe resulting from firing the wrong ammo in a firearm. The internet is full of such stories. Is it any wonder the ammunition companies are paranoid about cartridge interchangeability?
If you work with numerous guns, it's a good idea to utilize a few techniques that can help avoid ammunition errors. For handloaders who use plastic ammo boxes such as the wonderful ones made by MTM it's a good idea to use different colors for different calibers. And that's in addition to putting big labels on the lids as to which gun that ammo is for. Between the labels and the colors, I usually manage to grab the right box when I'm headed out the door. If you shoot factory ammo, and own several guns, it's important to keep the cartridges in the factory box, or transfer them to something like an MTM box that is properly labelled. Ammo in an unmarked container is a good way to begin a misfit situation.
If you're in the field and shooting only one gun, there's not much to go wrong in regards to ammo interchanging. However, when we go to the range, we might take several guns. Then more care is required. Get in the habit of keeping only one gun on your shooting bench at a time, along with the appropriate ammo. If you switch to another gun, ensure only the ammo for that gun is on the bench. I learned this lesson when I tried to chamber a .204 Ruger cartridge in a .223 Rem. rifle. Fortunately, it doesn't fit.
In summary, know your gun, know your ammo, and pay attention when the two go together. I don't want to be picking up more samples for my "What was that shooter thinking?" collection.