I've been told corn meal won't compress but the powder will. So the trick to getting a consistent load is
1.) have a way to measure the powder out so it's the same every time.
2.) make sure that each chamber gets the same amount of corn meal each time. Don't just wing it or guess. Don't tap or settle the corn meal (some people do some don't- I don't ... Much) until all the chambers have their fill. That way no one chamber gets settled more than the others.
3.) your seat depth needs to be controlled. Your press should have a stop on it that only allows you to seat the ball a few thousandths below the face of the cylinder. That way you seat to the stop. Depth and travel or jump is now consistent.
The key in any firearm be it black powder cartridge, smokeless, muzzleloaders, single shots, shot guns, percussion revolvers.... Consistency is the road to accuracy. But it only counts for a small percentage. The rest of it depends on the shooter. His stance, grip, trigger control, breathing, his mental state of focus, etc.
For the hobby shooter, the once in a while guy, dumping stuff down the chamber and crushing a ball on top with the guns loading lever is fine but if you want performance then you'll need to get scientific. Consistency is crucial.