As I expected, a lot of good advice here and I appreciate it all. By the way, this is the English rifle in question......
https://americanlongrifles.org/forum/index.php?topic=34719.0To fill in a couple of blanks, the barrel has round bottom rifling and I was using Hoppe's #9 black powder patch lube (very wet). The pillow ticking I was using is about 0.012" thick. I had some denim that measures 0.015 thick but did not get a chance to try it. The muzzle crown looks like this
So I don't think it is a crown or radius problem but the patch is almost certainly too thin and / or the ball is too small....or both. The recovered patches looked good but a few did have small cuts that looked like they were made by a sharp edge on the rifling. I will take pictures next time and submit them to you guys for forensic analysis...
As far as shooting skill goes, that was my first assumption.....that I had not been at this in a while and might be pulling my shots randomly. However, I switched over to the .36 caliber copy of a Jim Chambers rifle I had built a while back (
https://americanlongrifles.org/forum/index.php?topic=37186.0) and tried that for a while. Using a .350 ball, same ticking patch, same lube, and 40 grains of 3F Shuetzen powder at 50 yards, the rifle grouped well but about 3 inches left of center. I moved the rear sight to the right a tad, and the rifle shot point of aim for the next half a dozen rounds.
I know the English rifle will shoot well if I get all of this sorted out. I will repeat all of this and report back....and this time I will take pictures of targets and patches.
Thanks to all of you for your help.