I will qualify myself by stating that I have never owned, nor shot to any degree, a smoothbore muzzleloader.
That being said, I have been reading about them voraciously for many years now in anticipation of one day owning one. Progressive osteoarthritis in both shoulders says that probably isn't going to happen, but the dream persists.
Many posters will tell you that their weapon is capable of rifle-like accuracy out to (x-number of yards); some will tell you 100 yards. Others, will swear that no matter how much time they have spent on finding the right load, they just don't trust themselves to hunt deer with it.
Now, anybody that is in the know, is well aware that modern m-l rifle barrels that are poorly made/defective are quite rare. A rifle barrel that WON'T SHOOT is very, very rare.
So, why the seemingly HUGE difference in accuracy between modern smoothbore barrels, and modern rifle barrels when stocked up into a gun?
Number one, and my pet theory, is that the average modern smoothbore barrel is too heavy/thick-walled, which is somehow affecting the barrel's harmonics as the ball, or shot column, is traveling down the length of the bore before exiting.
People that purchase a smoothbore with a historically correct barrel profile as regards to bore size vs barrel wall thickness, virtually never complain about not being able to get their gun to shoot accurately.
Most barrel makers are using a single profile to bore out, and ream, 28 gauge, 24 gauge, 20 gauge, and 16 gauge barrels. A 12 gauge usually gets its own profile.
A lot of this has to do for the CONVENIENCE of the pre-inlet stock manufacturers. These companies DID NOT want to have to carry separate stocks in all of the wood types/grades for .32, .36, .40, .45, .50, .54, .58, and .62 calibers. So, they asked the barrel companies to "standardize" on the "A", "B", "C", and "D" letter profiles for rifle barrels that we have now. And, those letter profiles transferred over to smoothbores as the barrel companies compromised on bore sizes/gauges by just not rifling one of the larger rifle bore diameters that corresponded approximately to one of the smaller gauges/bore diameters.
Number two, is that there are far more variables in getting a smoothbore to shoot well, compared to a rifle. And, most posters having trouble seem to have difficulty just CHANGING ONE VARIABLE AT A TIME. If you change more than one thing at a time, then isolating what is giving you fits becomes FAR more difficult.
Third, and this does not seem to be talked about a lot, but I get the "sense" from having read thousands of these posts over the last 7-8 years, that most people having trouble getting their smoothbore to shoot well, ARE NOT keeping a high-quality, accurate, log book of what they are trying to accomplish.
Forth, is when someone here, or over on ALR, makes a suggestion of how to correct a perceived problem; the advice is often "interpreted" by the recipient of the advice. In other words, they chose to PUT THEIR OWN SPIN ON IT. Sometimes, the hardest thing to do is to follow someone elses advice EXACTLY.
You see this most often with the "SkyChief Load". Someone chimes in on a thread, or starts their own, to complain about the SkyChief Load not working at all, making things worse than their standard load, or only improving their standard load a little bit.
Come to find out, 99.999999999% of the time, they changed one, or more of the components in the SkyChief Load. Even when it states right up front, "Follow the instructions EXACTLY, and DON'T deviate from ANY of the components". People still change something, and then complain. The SkyChief Load is totally counter-intuitive. It makes NO SENSE, ballistically. But, it seems to work, if the recipe is followed exactly.
Fifth, and finally, smoothbores are "supposed to be finicky & hard to shoot" That's because EVERYBODY SAYS SO!!!. If you go into shooting a smoothbore thinking it's gonna be a ain-in-the-pass, then the chances are that's just what you are going to experience.
Nobody told me at 17 years old that shooting my first muzzleloader, a .45 caliber, flintlock longrifle, was going to be hard. That's because I was completely self-taught, with no mentor(s). Nobody to piss on my blanket, whisper into my ear to NOT FLINCH, when the powder in the pan ignites. I just loaded it, aimed it, pulled the trigger, got used to the lag time compared to a .22 long rifle, and never developed a flinch.
People hear, and read all these smoothbore "horror stories", and EXPECT to find it difficult to find a load that shoots well.
Having a positive attitude to start with, assembling as many component choices up front as possible before starting load testing, keeping an accurate log book, and only changing 1 thing at a time. These are all important things to do starting out with any gun, but especially with a smoothbore's many variables. And, knowing that you just might have to spend a year, many pounds of powder/lead, before you can feel comfortable at whatever your personal ethical range is for hunting.