That is spooky. I worry about .308, 7mm-08, 7.62x39 and .30-30 getting confused. I'm very careful about it.
I knew a guy that had a 20 ga. shot shell dropped in a 12 ga., loaded and fired a .12 ga. over it and lived through it. That's another thing I keep a close watch on. I keep all ammo seperated by caliber and plainly marked. Pete
I started hunting about 1970ish, which is also about the time the U.S. ammp makers all adopted the convention of using YELLOW paper or plastic when manufacturing new TWENTY GAUGE ammo. I remember in the hunter safety course I took at Fort Ord as a fifth grader, that specific danger was explained of having a left-over 20ga shell in one's pocket if they were shooting 12gagg.
Even as a 10y.o. I understood the whole "No-No!"
Some years later I figured out that many times the 12ga would simple shove the 20ga round down and out the bore, not always damaging the 12 gauge.
Just a 'bad shell' that really kicked hard.But it was when the 20gauge
also detonated still in that barrel along with 12gauge pressures that things came apart! Never knew anyone who personally did that nor knew anyone who knew someone else who did. Thankfully!
Also I worked as a sporting goods clerk in a SG store where one of our cutomers bought some WRONG ammo for his Browning BAR rifle in 7mm Mag. This was when Remington remarketed the .280 as the '7mm Express.' Sadly the customer bought the wrong shell, even after he was told what to "be sure to check for" before firing a round.
He didn't hurt himself - his rifle went BANG, didn't come apart, but he still ruined the gun.