Found it. The Ruskies made some 22lr Tokarevs, but they went about it in an odd way. They made a pistol, not sure if it's a conversion or a purpose built gun, that used 22lr in special aluminum sleeves that made the rounds look like 7.62x25. Here's a link to a page with a picture. http://www.securityarms.com/20010315/galleryfiles/1700/1746.htm
That brings up an interesting idea. Make a barrel insert that has the outer diameter of the neck of the 7.62x25 and an inner diameter a little smaller. That will keep the insert form being launched from the gun. If you want it permanent that wont be needed as you could solder the parts together.. It could be made from a unusable or irreparable 22 rifle barrel. It just needs a section good enough to cut off and turn on the lathe to the right dimensions. The insert would be covered in for instance,a couple layers of heat shrink tubing or something similar. You want something soft with a little give,but not much to avoid metal on metal contact of the barrel,but it still has to keep the barrel centered. It has to be a tight fit,but come apart when you need it to. The front of the insert that sticks out past the barrel would be cut down say,1/32 or 1/16 of an inch or so. It would the be threaded and a nut made so that insert would be installed,and the threads would not touch the barrel as it was slit through,then a nut (probably knurled and of a similar diameter to the barrel) would be screwed on to keep it in place. If it comes off,either a pin of some sort or set screw could be added,or just a drop of locktite.
Next,you will need the sleeves. I'm not sure if aluminum or brass would work best. I tend to think brass is a little easier to work,but aluminum is easy too. It would have a neck diameter sized of course to mate with the insert. The hard part would be firing pin. One question is whether a strike to the center of the cartridge would be enough to set it off? I'm thinking not reliably. If that's the case then you have to crush the rim. Another issue is that the cartridge could slide out of the adapter and it might not feed correctly. A way to solve both of these problems might be to make the back of the adapter unscrew. It would carry a little part that was shaped such that when struck in the center,it would crush the rim. It would have to be made out of something brass,and easy to make as it would tend to wear out and need to be replaced often. It might have a spring on it. You would put the cartridge in the adapter, and then screw on the top and load up the magazines. The down side would be that it would be a lot of work to load. Getting the firing pin to strike the right part of the cartridge seems to be the real challenge here.
