Just out of curiosity, is there a difference in chamber size between the 2? Wouldn't it be like shooting 22 short or long in a LR? I've never been tempted to do it, but I was just wondering.
.22 S/L/LR use a heeled .222" bullet.
.22 Magnum uses a conventional .224" bullet. It was developed from the .22 Winchester Rimfire (.22 WRF), which can be safely fired in a .22 WMR chamber.