Some years back, I bought a couple pairs of 3/8 groove-to-Weaver adapter blocks at the local gunshow. These have worked very well, allowing me to use scopes on a couple Norinco .22 rifles (Chinese-copies of the BRNO action) that had bolt-handle-clearance issues with standard scopes. They mount to the gun's grooves with set screws. I haven't seen them in awhile, so I don't know if they are still made/sold? I'm thinking Tasco made them at that time.