Like Rifleman1776 said, "The only "proven" load is the one that works best in your rifle gun."
I'm sure you've heard about identical rifles which are fussy about the ammunition they are fed.
.22's are famous for this.
So are muzzleloaders.
Two identical factory guns, shot by the same person on the same day at the same range will be quite different when it comes to accuracy with any given load.
One might like a .440 diameter lead roundball patched with a .015 thick cloth patch over a 65 grain powder load of 3Fg powder. It will shoot the ball into a 1 inch group at 50 yards.
The other rifle might not shoot that combination better than a 4 inch group at 50 yards.
Although it doesn't like that powder/ball/patch load, that same gun might shoot a different powder/ball/patch load into a 1 inch group at 50 yards with ease.
You never know until you try different combinations.
Although some modern cartridge shooters who want a "Good out of the box gun/load" might consider this to be a large PITA, we muzzleloader shooters gladly take up the challenge to find the "best load".
I mentioned a 1 inch group at 50 yards and to newcomers who have heard that "the old fashioned muzzleloaders shoot poorly at best" that might seem to be an optimistic goal but it's not.
These guns can be very accurate once the right powder/ball/patch load is found.
Just to add to the fun, after a good ball/patch combination are found, almost all muzzleloading rifles actually have two powder loads that give the best accuracy. Usually, one powder load will be a little better than the other but one will be on the "light" side and one on the "heavy" side.
For instance, your rifle might shoot a 50 grain and a 80 grain powder load very accurately.
Powder loads in between these might be fairly poor.
I mention this because you mentioned shooting silhouette matches out to 100 yards.
Roundballs loose their velocity and energy rather fast so for shooting at long range you might need the hotter powder load if you want to knock down metal targets.
Oh. While I have your attention, the synthetic black powders leave a lot to be desired.
If you can find any, try to buy real black powder.