I'll add to Daryl's reply,
There can be no glare on the sights.
Your eyes must be good enough to see definition between the sights and target at 100 yards.
Your rifle, loading technique and chosen load must be consistent every single shot.
My locks are tuned and polished for maximum speed and consistency.
Here is the tough part, the shooter must be capable of shooting small groups with a flintlock rifle. Tiny groups with a percussion or CF don't count. The flintlock will bring you back to earth because shooting a flintlock is a learned process and entails more than other rifle types.
Don't take this the wrong way, I'm only mentioning this for your own good and have been through the learning curve myself. You mentioned earlier that your new to Flintlocks, so right off I don't think your ready to shoot your best groups with a flintlock.
So far you have attributed your accuracy problems to humidity, patches, lubes, shooting with the RR in or out, etc. But not once have you taken into consideration the shooter might have a lot to do with your problems. You have to really learn to concentrate, more than you think is necessary, and to follow through. For example: I don't even see the smoke I'm so focused on the front sight, and when the smoke clears my front sight is still on the target. It takes A LOT of practice to get here.
You still have the flinchlock flinch to some degree. Even just a small amount will open up those groups. To shoot your best you gotta beat the flinch.
I have no doubt you and your rifle are capable of those little groups your after, and I know it can be an obsession. Because I have it too. Regardless of the weapon I can't be satisfied until I get it shooting those tiny groups. I don't shoot at 100 yards with a ML much anymore but I did when I was much younger. In the mid 70's and 80's all I had was a .54 Renegade with a 26" barrel and it consistently shot 3" groups off the bench at 100 yards. I won a lot of matches with that rifle.
The last (only) time I shot my .40 flint at 100 yards I had a bad glare on the rear sight yet it still turned in 3 to 3.5" groups.
My advice to you is keep practising, a quality shot each time. Analyze both you and the load and rifle to find the root of the problem, then work on it until it's fixed. You are building both muscle and mental memory and that doesn't come overnight.
I work out my accuracy loads at 25 yards to find the most accurate several days in a row, then I move back to 50 and do it again. The best one's I would test at 100 yards.
I am attaching a photo of a sighting in group shot last fall with my .54 Haines, this rifle will do this consistently. If not then it's my fault not the rifles. You decide if a Flintlock rifle can be accurate.
how do i delete