Thanks to everyone who sent me information. Even the factory suggested calling JJ Perodeau for help. JJ gave me the secret to getting the two halves of the receiver separated, brute force! Once the pins are removed you have to pry the trigger plate unit from the top of the receiver. As I suspected, a tiny metal shaving was jamming the plunger that fits in the front of the top lever keeping it from locking open. Now, back to shooting. If anyone needs to take their Chapuis double apart PM me and I'll walk you through the tools you need and the procedure.

Bob, it sounds like you are more more skilled and capable of handling such a problem than most of us! I wonder if JJ needs an assistant? :-)

JJ is brilliant! He has the picture of the rifle in his head like files on a computer. I'm just poor and have had to learn how to figure things out for myself.