Gagde;
I've discovered that the problem is the Wisner springs. The problem started after I sold the gun to a good friend of mine, who took it to the local gunsmith to be cleaned. He also suggested the springs be changed and did so with Wisner springs, then the upper barrel started misfiring, three more trips to the gunsmith and it was still misfiring. So I brought the gun home to work on my self. I removed the spring and did a tracing of it, then ordered a new spring also for Wisner. When it arrived I compared it to the removed spring and discovered the new spring was about 1/4 higher.
Put the new spring in place and everything was fine for about 20 shots, then misfiring started again. I removed the new spring and compared it to the old one, the profiles were exactly the same. My conclusion is that Wisner are not heat treating their springs properly, and of course the original springs have been discarded, so I'm at a loss for an answer.
Bob