Hello Mike StL,
I will share this in the spirit of being helpful, not critical. I believe that you need to work on your load in both cases.
A 50 yards, I strive to get three or five shots touching off the bench. My eye sight doesn't allow me to do that every time, but I am working for that. In your case, I am seeing 2.5" to 3" bench-rested groups at 25 yards. That would be a large 5" to 6" group at 50 yards. Your "reasonable" accuracy may be different than mine though.
My suggestion would be to circle back to the basics, and focus on changing one thing at a time. Ladder up your charges five grains at a time, and see if your groups tighten. You never know with rifles, but that charge for a .54 seems a little light for a best accuracy load. It may be what your rifle likes after checking, but I believe it is worth a try. I listen for the rifle report to change from "Pop" to "CRACK!" to know if I am approaching an accurate load.
In reading the patches, I am a little surprised on first blush at how the thicker patches are that black. I am wondering why. A .535 ball with a .017 patch should work well if the weave is strong and tight. Yes, that load will be tight going down. 2f is traditionally considered for a .54 accuracy powder, but many get good results with 3f. It might be worth testing 2f in your .54 to see if things improve.
That points me to your patch lube. Perhaps give a try wet-lubing with Mr Flintlock Lube or the super-slippery Hoppes BlackPowder Cleaner & Lube. Either is really good, and may improve things. Again, I'd change one thing at a time and test. My first change would be your patch lube.
Your second group is showing you things. Your patches are way too thin at 0.010", and are getting blown apart. No need to test that any more. Frankly, a well loaded smoothbore would beat 2.5" to 3" at 25 yards.
.52" ball plus .010" patching on each side gives you .54" total. Your grooves were not filled at all. Assuming you have, say, .012" grooves, you have .54" bore plus .012" groove plus .012" groove = .564" to fill with a .54" patch and ball combo. You are not sealing at all, and your charge is blowing by and destroying your patches. This blow-by of gasses means erratic and lower velocities, shown by you group printing lower on target. If you are using something like deep-grooved round-bottom rifling, you'll need even thicker patching. In any event, toss that .010 patching as it is not helping you.
Your .535 ball and .017 patching combo gives you .569" combined, in a bore that is .564" if you have .012 grooves. So your thicker combo is sealing, but not in an extravagant manner.
Again, I'd try changing your lube first, and you may find it loads easier with the same .017 patching. Then I'd ladder up the powder charge and test for accuracy.
This was the first five shots out of a clean barrel at 50 yards, and I was happy with that. Shot #1 was the one out of a clean barrel that printed out of the group. I wish my eyes could do this every time. I was testing a wet lube on this day, and the barrel liked it a lot.
These patches from The Minute-Men patching company look like I'd expect when cut at the muzzle. My test patching passes the test when I cannot see sunlight through a fired patch. The Minute-Men patching always passes the test. It is a very densely woven canvas. I buy their untreated (versus teflon coated) patching, and wash it before use.
This is how to find The Minute-Men patching. The website does not work, but he answers the phone in the evenings.
I hope all of this helps a little. God Bless, Marc
