Clean the barrel between shot. You can use spit on a cleaning patch- just wipe the patch on your tongue- no need for a big wad of spit on it- to pull out the cake that builds in the barrel. Then run a dry patch down the barrel to make sure its dry, before pouring in the next powder charge.
Loading a Muzzle Loader is not a quick fire deal. Deal with it. Accept it. Don't try to bend the rules. These rules don't break very easily, and getting a stuck ball out of a barrel is a royal pain. If you insist on seeing how many shots you can fire out of your barrel before you can't get another ball all the way down to seat on the powder, do it at a range, and not in the hunting fields. This is one " test" that has been done over and over again by thousands of new shooters before you. I would hope that just once, one of you new guys would simply learn from our mistakes and just clean the barrel between shots.
Yes, there are some guns, and some lubes that let you shoot without cleaning. All day long. You will hear from Roundball I am sure, as he is very proud that he can shoot all day and not wipe his barrel. He should be. His barrel is a rare event, but he doesn't have the experiences with other gun barrels, fired in other areas of the country with different relative humidity, and temperatures than he experiences in his home range.
I have had a few guns that stayed very clean except for the last few inches of the barrel. The amount of lube on my patch just wasn't enough to lube the entire length of the barrel, and crud built up towards the muzzle, while once you got past it, the fouling was very soft and easy to clean out.
Other guns stay cakey all the way down to the breech, and so far the lubes I have tried have not made much difference in how hard the cake is. I thought Bore Butter was the answer, but I met my match with a gun that just wants to cake up, even with liberal use of bore butter.
You don't have to jump off a cliff to know that the sudden stop is going to hurt! I think the same way about cleaning ML barrels frequently. If you don't do it, you are going to get hurt, with a ball stuck half way down the barrel, powder in the barrel, and no cleaning fluid or solvent along so that you can pour it down on the PRB and loosen the crud around the Patch, so you can at least run the ball down on the powder and then shoot it out of the gun to give you access to the entire barrel for cleaning. Simple water will loosen up most stuck balls, but too much of it, will seep around the ball and neutralize the powder. Then you do have to pull the ball, and dig the soupy powder out of the gun, dry the barrel, the flashchannel, and the powder chamber in the breech if there is one, before you can reload the gun for the next shot. Do you really want to be doing that in the field because you are unwilling to take the time to clean the barrel between shots? Does this not seem to be the lesser of the two evils?
The ML rifle in your hands is a single shot weapon. That is all you should expect to get at a deer. Most deer are not going to stay around while you reload, no matter how fast you can do so. So, pick your shots at game, turn down shots that might not get through the brush to the deer for a killing wound, and join the rest of us who talk about the big one that go away! You will like yourself so much better.