Is there some reasonable explanation for why we had to make them so different and stick with it this whole time???
I don't know about reasonable, but I was around when the new rimfires came out in the high-velocity race of the 1960s, and the .22 magnum is the only successful new rimfire of the 20th century. The .22 WRF dates back to the 19th century when the number of rimfire cartridges was large and varied.
They picked the .22 WRF diameter as something they were already tooled up for that would for certain NOT fit into a .22 LR chamber.
Having someone put a high pressure .22 into one of the millions of old (up to 100 years) .22 LR chambers and blow themselves up was a major worry.
Other solutions like the bottleneck 5mm magnum died.
In my .22 magnum rifle, the .22 WMR is good for varmints and breaking turkey necks, while the WRF with its slower 45gr lead bullet takes squirrels out of 150ft trees without blowing off major body parts. The difference between the accuracy of .22 WMR and .22WRF is academic to hunting. IMHO, the .22WRF is one of the best rimfire hunting cartridges ever made.
The idea of having both .22 LR and .22 WMR in the same gun was sort of an afterthought, and accuracy does suffer for the one that does not fit the barrel, but again, for coon-hunter accuracy, not so important.
There were several cheap imitations of the Ruger single six convertible with 2 cylinders, and the Ruger itself was pretty cheap in 1965. I have a fixed-sight convertible that I only shoot with .22WRF, because the .22 LR and .22 WMR do not shoot to point of aim.
The idea at the time was to have a rimfire .22 of about .22 Hornet centerfire power. Since the .22 Magnum is still around, I guess enough people liked it. Keep in mind that it was to be a hunting round and not a precision target round and the result makes a lot of sense. My .22 WMR rifle has a barrel cut specifically for .22 magnum, and the acuracy is exceptional--especially for a rifle I bought used for $40 in 1965, with JC Higgins scope and sling.
