Here's the video I was looking for-
the LUGER- Tales of the Gun
A very good documentary I have listened to several times now.
https://www.youtube.com/watch?v=ImjKpf3M_1k
At minute 39.45 starts a short commentary about taking the only surviving vintage 45 cal Luger P08 (the spare gun taken to the 1907 trials, serial no 2) out to the range and firing it.
As the commentator states, "If a part breaks, there's not much you can do about it!"
THAT must have been a unique experience.....