I shot some .22LR in my .22Mag cylinder once, by accident and while I didn't have any split cases, what did tip me off to the fact that there was something wrong was the debris and sparks coming out of the cylinder gap. It wasn't a ton of stuff, but it did make shooting it unpleasant and weird. It also didn't take many rounds to warrant an investigation, and that's when I discovered I had the wrong cylinder on the gun.
I've shot a cazillion .22 lr from my .22 mag. Other than hard to eject from the swelled cases, its no biggie. Lots of internet Bullcrap about this subject.