Regarding rebounding frizzens, in teh 80+ videos I have, the only lock that did no rebound was one in which the frizzen came down on David Prices thumb. We watched many times to see what was different and then saw the frizzen/thumb impact.
An interesting test was suggested by Lowel Gard (bevel up). We used his Chambers Late Ketland, starting with a fresh flint. We videoed try 1, 11, 21, 31, 41, 51, and 61. Lowel snapped the lock 10 times in between. In watching the rebound, I noticed that the rebound grew slightly as the number of tests went on. It never hit the flint, but came closer as the flint gradually grew shorter. After thinking about this my conclusion was:
As the flint shortens, the flint contacts later and farther down. Because it is traveling farther, it isfaster, it hits with more force. The frizzen opens more forcefully, and impacts the spring with more force. The spring conmpresses more and rebounds slightly farther.
Regards,
Pletch