It's less than half a second with a good lock and flint as long as you keep it clean. That's still enough time that you have to have good follow through. If you can shoot a flintlock well, you can shoot anything well.
Here is my rifle, along with my shooting bag, new horn, and old horn. The rifle is a Pedersoli Scout in .50 caliber. It's not a proper longrifle, as it only has a 28 inch barrel. One of these days I will buy or build a proper one. The shooting bag I made myself. The fur is from the first deer I ever killed. It was also made using period materials. Interestingly enough, the black color is not from dye, it is from a chemical reaction using what is called vinegaroon. The other powder horn was "made" using a cheap pre-made horn and then extensively modifying it. The new one is the first I've made from scratch. Hanging from the old powderhorn is my powder measure and vent pick.