This is a complicated process, but it's based on the burning characteristics of blackpowder and blackpowder substitutes. That is why it is crucial to ensure the projectile is firmly on top of the powder. One way to do this, once you have figured out what load works best with your rifle, is to mark the ramrod. There are two ways to do this. You can take a pencil and mark a ring around the ramrod at bore level once you have rammed the projectile down the bore.
Some people like to use a pocketknife and lightly score a ring that way.
If you change your load, you only have to sand lightly to remove the mark and mark it again. Marking the ramrod makes it very easy to tell if your projectile is down where it should be since you need only look for the mark on the ramrod. Once this is done, you prime your weapon with either a percussion cap or priming powder for flintlocks, and the rifle is ready to fire. Our sport can be a safer one if we all take the time to gather all the knowledge we can and sort it out. There are many knowledgeable people who are more than willing to help.