falcon, that Bushnell I mentioned was exactly the same. Near the limits but held just fine for a long time, then went haywire. Back to the center of the adjusment range and alll was well again. Bushnell told me that I had exceeded their 20 minutes of arc limitation [:-] ?? I had never heard of such a limit prior to that communication, and it seems insane that a scope maker would provide adjustment range beyond a scope's ability to hold zero solidly, but that was what they told me.