I know that when I shoot my flintlocks I think that I can detect a slight delay. If I let someone else shoot my flint lock rifle, I don't hear any delay.If your interested, those high speed camera tests were done by one of our members. Check out the posts on the forum made by a man called Larry Pletcher.
He ran the tests and wrote the articles.
Here's a link to his home directory where you can find a list of posts he's made.