I have an old remington 550 (I think) that is a tube fed semi that will reliably cycle s, l, lr. It does this with the help of a floating chamber. (I haven't noticed any pitting and its a very old gun with probably countless rounds through it).
Got pics? Where'd you find it?
...but why not CB longs in a gun marked LR only?
That's probably a general problem for .22cb, .22bb's and .22short in general.
I have a match barrel and tried to solve the Stinger myth. When I had the barrel out of the rifle, I took a Stinger and it slid right in, no force required. I have a feeling that all match barrels accommodate the extra MM. or 2 for Stingers, but people still believe the old wives tale that it is a horrible idea, without actually proving whether it is true or not.
My advice is to prove it for yourself first, ask a guy at the range who's shooting Stinger 22's if you can borrow 1 Stinger round to see for yourself.
So my question is why can you not shoot long or shorts in a long rifle 22. Magazine issues aside I can see not using ammo that is to long, eg. stingers in a match chamber, but why not CB longs in a gun marked LR only?