"Change", makes it happen. If everything stays the same, the results will be the same.
Every time you shoot and get good results, you need to know why and repeat it. The three things I pay attention to, are clean, dry, and consistant.
You start with a clean and dry barrel, clean and dry frizzen,and a clean and dry flint. You also have a sharp flint tightened and positioned consistantly.
You add the proper type and amount of powder, and patch and ball and push it down against the powder, but not compressing the powder, to a mark on the ram rod, (consistantly). You place the powder in the pan and shake it toward the flash hole then level it back in the pan, consistant to what you always do. By this time you should know how to position the flint, and be as consistant in positioning it as possible. There will be more varables with the flint, due to the shape and nature of the flint.
Now you fire the rifle, and everything went good. Well, everything just "changed", now the barrel is dirty, the pan is dirty, the flint is dirty, and duller, and may have loosened or changed position. Mean while, the moisture is attacking the residue in the pan, the barrel, the frizzen and on the flint.
Here is where you must return the rifle back to it's original state of clean, and dry. You can wipe the pan, flint and frizzen and do the best you can. Pick the flash hole and clean it out. Wipe the frizzen and flint. Check the flints edge and position. While in the field, you will never be able to return it back to it's original state of clean and dry, but you consistantly do the best you can, and hopefully get more ka-booms, than swoosh-boom.
That's my take on it, your milage may vary.