Let's look at SAMMI specifications:
It's interesting to note the spec for bullet diameter is actually larger for .22LR (.2255 -.004) than for .22WMR ).2245 -.004). These are the official SAMMI specs. The bore diameter for .22LR is .217, groove diameter is .222. For .22WMR the bore diameter is .219, groove diameter .224. I have read (on the interwebs, so it must be true) that gun manufacturers are sometimes a bit lax in complying with SAMMI specs, so take it for what it's worth.
So groove diameter for .22LR/.22WMR is .222/.224, a difference of two thousandths of an inch, roughly the thickness of a human hair. A .22LR fired in a .224 barrel will obdurate to fully engage the rifling. (Remember, .22LR bullets are either bare lead alloy or copper washed, not jacketed) OTOH a .22WMR fired in a .222 bore (assuming the chamber was reamed to allow it, though I wouldn't want to sit next to someone dumb enough to do that) stands a good chance of causing possibly catastrophic failure, since .22WMR bullets are jacketed just like CF bullets, and that copper jacket is not going to like being squeezed down that much.
On a related note, while firing a .22LR in a .22WMR chamber is possible, it's also asking for trouble. (Hint: Google is your friend.)