I have experimented a little with the Erma .22 lr conversion kits, both the pre-war and the 1980s SE/08-2 version.
Overall I'm not impressed with the quality of the sets. They are prone to jamming and getting one to work flawlessly is almost impossible. The first set I tried, which consisted of a mismatched barrel / toggle combination worked well until the barrel freed itself from the chamber. It appeared that Erma hard soldered the barrel bit into the chamber part, and this worked loose over time.
The next step was to replace the barrel (after some failed attempts to repair the other one). But this produced an interesting side effect. Although the barrels are both numbered in the 4000-range, they are actually different in a critical area, the position of the chamber is higher on the replacement barrel, causing the .22lr rounds to strike it's edge. 9 out of 10 rounds will stick and have to be refed manually.
The second set, the SE08/2 works slightly better (barrels are not interchangeable between sets), but the toggle refuses to close fully 9 out of 10 times.
Period documentation suggests that the German army and police also had issues with these sets, it was ordered to mate the sets up with one particular pistol and keep the set and pistol together. Which suggests that these sets do require a certain amount of fitting and fiddling around with to get them working with a particular gun.
If you want to shoot .22lr with a luger-like pistol, get a Ruger
