The relationship between the .22 LR and .22 Mag (.22 WMR) is not like the .38 spl and .357 mag, where the .357 is just longer. The .22 LR uses a heel based bullet meaning that the diameter of the bullet is about the same as the case itself with a smaller diameter "heel" to fit in the case.
With most rounds, the diameter of the bullet is smaller than the case such that no part of the bullet is the same diameter as the case. This is important because the .22 Mag uses a non-heel bullet. Therefore, to fit the .224 bullet, the .22 Mag case is .242" while the case of a .22 LR is .226. That's a significant difference.
It can be done.
I've seen[STRIKE] people [/STRIKE]dumbbells do it.
The cases split and gas blows out of the back of the cylinder.
It's dangerous and stupid...
Don't do it. I have seen it done several times on the range. As stated above split cases, lots of blowback and terrible accuracy. People try it because they do not want to buy the more expensive 22 mag ammo
I didn't see how this could destroy a gun but I guess if you did it enough, you would eventually have gas cutting from the brass being split every shot.
So I guess it can destroy a gun... I wouldn't have assumed it was any worse than putting a .410 in a 45-70 to use in a pinch. Of course that isn't a good idea to do very much either, but there's not much way it could blow up the gun. Don't think a 22lr is going to blow up a 22 magnum either, really, but with excessive use I do see gas cutting becoming possible.
And yea there are cases where you MAY want to drop a 410 in a 45-70... If you don't have a 410 but encounter one or 2 snakes a year and happen to have some birdshot sitting around. So just giving the reasoning there.