Grumpa,
I hope we have not confused the heck out of you. To get the smallest groups possible when firing long strings of shots, there has to be a combination of having the most accurate load for your gun AND knowing how to get the most accuracy out of your gun when doing so. So in this post, I will attempt to explain how to do the latter.
As a young Sergeant and before I knew who he actually was, Carlos Hathcock taught me to sight in a bolt action hunting rifle. He told me to make sure the bore was clean and have the ammo I would use for hunting and meet him on the range. He made me lay down and take up a good prone position. He told me to take my time and concentrate on firing ONE good shot AND make sure I knew where it hit. After I fired it, he scoped the shot and asked how the shot looked when the rifle went off. I told him it went a little high and left, as I remember. He grinned and said, "Good Call." He adjusted my scope and bit and then said, "Now clean and dry that barrel thoroughly and meet me back out here tomorrow." The next day we repeated the above and after the shot was fired, he adjusted the scope a bit more and once again told me to clean the barrel and meet him the next day. After some time of doing this, my Gunnery Sergeant (who had set it up for Carlos to teach me) asked how it was going. I told him it was going well, but we were only firing one round a day. My Gunny then said, "How many rounds do you think you will get when hunting?"
To make a LONG story short, Carlos had me shoot ONE shot from a clean barrel many times over different distances and weather conditions. He had me record everything possible about time, temperature, wind, humidity, light conditions, scope settings, how I felt that day, etc., etc., etc. He even called me up after we had finished most of the shooting on a COLD December day when there was 4 inches of snow on the ground and it was raining freezing rain. When I was somewhat hesitant, he asked "What happens when you have to hunt in this weather?" OK, so out we went. The Log Book I had for that rifle was so complete I could set the scope for any range I was going to shoot, in almost any weather condition and was SURE the first round out of the rifle would hit exactly on target. This is often referred today as shooting with a "cold zero" as someone else mentioned. Even before that I had read where the FIRST shot out of a cold barrel would often or usually go outside the group with other guns. That is fact.
OK, I hope I will be forgiven mentioning shooting a modern rifle, BUT there is much to learn from this for muzzle loading.
John mentioned how they took a "fouling shot" when shooting .22 rifles and SOMETIMES at some events, you can take a "fouling shot" with a muzzle loader. Unfortunately you can't do that at every event. Someone else mentioned cleaning and cooling the barrel between shots, BUT in some or many events, you don't have time to do that. So you have to tailor this knowledge to how you are going to shoot the gun, to make it useful.
If you are only going to fire one shot, as in hunting, then the cold zero method is the best way to sight in your gun. But what happens when one has to fire five, ten or 13 shots in some matches? Then it is best to PRACTICE with your gun the way it will be shot in the match and record where you thought the shots should have went and where they actually went. Also, note when you made mistakes on a shot. As others have mentioned, perhaps the biggest thing to get the most accuracy out of a gun is uniformity or doing everything as close to exactly the same way both when you load and when you shoot.
I suggest beginning practice from a clean/cold barrel since many matches don't allow us to fire a fouling shot. It is a good idea to run a clean dry patch or patches down the bore to remove excess oil first, before loading your gun. (This can be done before starting a “Woods Walk” or any other match.) Carefully load your gun and take up a good, uniform shooting position and fire the best aimed shot you can. Before you look at where the bullet hit the target, write down where you think the bullet should have hit. If you believe it was a good shot, then scope or check the target and record the shot and how far away it is from your normal group. If it was not a good shot, then clean the barrel and allow it to cool and start all over. What you need to know is how far off the first shot will be from a clean cold barrel compared to other shots you will fire in your group, SO you can aim differently for the first shot so it will go inside the group of the later shots. If for example you learn the first round hits a bit high and to the left from the clean barrel, then you aim a little low and right to compensate on the first round. I would call it a VERY successful practice session if all you learn was how far off the first round hits the target and you learn how to “hold off” or adjust your aiming point for that first round so it will strike inside your group.
Once you learn how far to hold off for your first round, then practice should be done the way you will shoot the match. IF you have time to clean or wipe between shots in a match, then make sure you do that as well when practicing. If you don’t have time to clean or at least wipe down the bore with one dry patch between shots in the match, then that is the way you should practice shooting for that match. After taking the best aimed shot each time, record where you think it went before you scope or find out where it went. Then also write down where it actually went and anything like an error or change in conditions that may have caused the shot to go out of the group. Once you have recorded the information from a few practice sessions and you note trends in how the groups open up as you shoot, you can also adjust your aiming point for the later shots in a string, to shoot a smaller group.
To record this information, you will need some kind of shooter’s log book. In my experience, it is best if you have a drawing of the kind of target you shoot and have two of these targets on each page. One is for plotting the shots after you shoot and the second one is to plot where the shot actually went. You write the number of the shot on the first target where you thought it went and then that same number on the second target where the shot actually went, after you scope where it hit. You don’t have to buy a shooter’s log book as you can make your own pages for the target, range and gun you will be shooting. Then copy the blank pages down and put them in a 3 ring binder. Here is a link to the sort of page I am referring to for an idea on how to make up your own pages.
http://downloads.bisonballistics.com/NRA-Highpower-Data-Log-Book-Prone-600-Zoom.pdf
Gus