Why is the .22 WMR rimfire cartridge is .224 in diameter and not .222?

Your mistake is at the start. There are no rifles that can handle both 22 LR and 22 WMR, except those that switch out the entire barrel. The length of the case, and the bullet diameter, are not the only differences between the two. 22 WMR is based on the long-obsolete 22 Winchester RImfire. It isn't a longer member of the CB/22 Short/22 Long/22 LR family.

Check your facts before you get all worked up...you are getting worked up on two points in which you are wrong...

1. "handicapping to a 22lr rifle that is able to handle WMRs too (some can) " -- Wrong. Name a single rifle that uses both cartridges without changing the barrel? You can't because the chamber sizes are still different. The only guns that can shoot both are revolvers that allow you to swap cylinders.

2. Don't believe everything thing you see in wikipedia. In fact there is plenty of allowable overlap between the two.

Here is the official SAAMI rimfire specs:

http://www.saami.org/specifications_and_informatio...

Note that the the allowable range for .22lr bullet diameter is: .2215 to .2255

And the range for .22WMR is .2205 to .2245

So you see they can both can be either .222 or .224 and anywhere in between and a little more on either side.

Why doesn't a damn chicken have four legs?.... now that would be a good thing.

It was designed to use the same pill that is used in other centerfire cartridges like the .223 rm or .22-250