The expression "a flash in the pan" is still used to describe a person or enterprise that shows promise, but fails to get past a good beginning. Under the best of circumstances, the flintlock system gave only reasonable reliability. A small piece of cut flint held in the jaws of the hammer struck a steel cover on the pan called a frizzen, knocking it open and scraping the inner side to throw sparks into the powder charge in the pan.
In terms of speed it was slow. Anyone who has seen a flintlock fired is familiar with the puff-boom! sound of the report as the priming charge burns with a one-beat pause before the propelling charge fires. History is filled with untold numbers of targets, animal and human, who have ducked to safety during that beat, which was sometimes two beats if the day was damp and the tube to the barrel a bit clogged.
Click here, or the headline link, to learn more about the history of primers.