Maybe I can start this thread off.
Bore fouling results from the combustion of black powder. Roughly 56/57% of the volume of powder burned, results in solid fouling.
Much of this is blown out the muzzle, but that which adheres to the bore lining, is what we have to deal with when reloading.
A too-loose or too-dry a patch and ball combination will result in the accumulation of fouling, shot to shot which will inhibit loading
and wiping/swabbing/cleaning/patching the bore will be necessary to continue to load and shoot. Having to do this 'cleaning' by
one of it's many names can introduce a problem of it's own, that of pushing some of the fouling down into the breech where it may
interfere with ignition of the next charge.
If using a combination that actually reaches to the bottom of the grooves "at least" and at best shows some compression in the bottom
of the grooves, along with a wet enough patch, the resulting fouling, shot to shot, will not be allowed to accumulate, shot to shot and
thus loading remains easy for an entire day's shooting (depending on the condition of your bore, of course). A rough bore will collect and
built fouling, regardless of the combination used.
If the ball and patch does not fit well, shot to shot velocity and pressure will be varied more than it should and as a result, your accuracy
will not be as good as it can be.
"When you load the next one, you clean the last one", so there is never any fouling buildup in the bore. There will be some at the breech,
which does not appear to effect accuracy in the slightest.
Patched ball picture from Lyman's Black Powder Handbook - It is as relevant today, as it was in the early 70's.