ggggr... thank you again for your generosity, I am grateful. I've finally taken some of my scant spare time away from my new Brocock Atomic (thing is fun!) long enough to dismantle the Tempest and check it over, and found absolutely no wear of any significance on any part. Putting it back together by the manual, step by step, I was doubly careful to observe each element carefully and reference your contributions here at the same time. And it works. All I can think is that somehow I misaligned the sear... though why it would work for well over 100 shots, then start failing, then fail completely is a mystery. But it's working well now, so all my pistols are happy at the same time. Hurray!