Hi HPT.
When I was making barrels I did an experiment using different twist rates for the same caliber. Nearly all my test was done with 50 cal, but the principals are the same.
I found that the rate of twist was the least important thing to consider in shooting round balls. Just the opposite of what I had read, and what I believed to be true, but the facts showed me other wise.
I made barrels with twists as fast as 1-12" and as slow as 1-104". All were lead lapped to a very smooth internal finish and would gauge within .0002" from breach to muzzle.
All were equally accurate.
What did make a big difference was the geometry of the cutting heads. In other words, the geometry of the grooves and lands themselves.
I never found that any barrel rifled with grooves as wide as the lands shot as well as barrels with wider grooves and narrower lands. Also the grooves must be at least .007" deep, but when you got deeper then .014" patching becomes a problem. I did one with .020" rifling and the only patch I could get it to shoot well with was thin leather.
So my advice is to never use a barrel with rifling deeper than about .014" and I personally prefer about .008.
WW metal can be hard enough to cause tight fits if the patch is to thick and it makes the compression of the cloth very tight. So I like .008 to .009 and a .014 patch for most of my barrels.
If you go a full caliber size small (.440 for a 45, .490 for a 50 .530 for a 54 and so on) the patch material you can get at most outlets is easy enough to load, and yet is still seals without cutting.
If you get any slippage between the patch and the ball one neat trick is to roll the balls on a piece of plate steel with 80 grit wet-or-dry glued to it. Gives the balls a slight texture and that grips the ball very well.
WW balls are just as accurate as soft lead if the casting is done right and they kill game so much better than soft balls. You have to see the difference for yourself.
It's common for 50 cal rifles with WW balls to shoot through elk and leave exits.
But 54 cal soft balls often do not exit a deer. Probably about 1 out of 2 on western mule deer has been what I have seen over the past 50 years with soft balls. On deer, when you get to 58 cal and larger the soft balls are fine just because they are heavy enough to go through even if they flatten into disks. Air dropped WW is about 12-13 BN. Pure Lead is about 5 BN. WW balls will break elk bones and flatten just a bit but not much. Pure lead will flatten extremely on muscle, and bones often tear it apart.
All the old timers said the same thing, but in the 1820-1880 many did their hardening with Mercury.
THAT'S VERY BAD NEWS. DON'T DO THAT!
Mercury is poisonous and when you heat it it becomes much worse.
Use ordinary WW metal and you get the same results on game with mush more safe casting.
In nearly all good quality barrel, if you are not getting good accuracy the problem is the patch in about 19 cases out of 20. Also remember that water based lubes are good for shooting soon after you load, but they will dry out if left in the barrel very long and that can also cause accuracy problems
One way to test your patch is to use a wadding patch.
Simply take one of your shooting patches and run it down the barrel over the powder charge, and then seat your patched round ball on top of it. That way you have a thin wad over the powder. If the accuracy improves dramatically that shows you that the single thickness you are using is too thin or too loosely woven, or it's not matched to the ball. You can go to a thicker patch, a harder weave, a wad, or sometimes going to a different powder (2f from 3f or 3f from 2f) will cure the problem.
If the patch is cutting at the rifling you will not often get good accuracy, and the very worst is when the lands cut only a few of the places on the patch instead of all of them. Believe it or not, that how it usually goes. If all are cut the accuracy is better than if only a few are cut.
Using a buffer on top of the powder ( a wad by any other name) is a good test because it buffers the patch, not the ball. If the accuracy get better that means the patch you are using is not doing the best job.
I typically get about 3 to 3.5 MOA from my rifles. I have made a handfull that would do better, and 3 I can remember that did a lot better, but 3.5 MOA is pretty common.
I used to be a very good marksman when I was younger, and I still cam make a very accurate rifle but at 60 and with my aging eyes I have to get a few of my young friends to prove it these days.
I made one that I shipped out about 2 weeks ago and I zeroed it at 75 and 150 yards. It had a standing blade rear sight with a 2nd folding blade for the longer range.
The day I did zeroed the sanding sight blade I had a good day, and the sun was out, no clouds, no wind and I felt very good about the group. I had it centered, and got 3 balls within about 1-1/4" and 2 out making the group about 2" overall. I smiled about that.
The next day I wanted to zero the 150 yard blade, and it was all I could do to keep them inside about 12 inches at 150. I was lucky to have a young friend come over and help. He is home on leave from the USMC and is a scout sniper. He's only 25 and can shoot very well. He shot the rifle at 150 yards and got 4-3/8". So I know the rifle shoots fine, but this 60-year-old-has-been just can't do it on demand any more.
Getting old ain't for kids!
I still do quite well with a scope, and fairly well with a peep sight, but with open irons I have trouble now days. And a scope on a traditional muzzle loader is about as welcome as Obama at the NRA convention.