Silk patching may be passable in a rifle with with shallow rifling (silk material is usually thin) but this is mostly Hollywood. The difference in force required to load a silk patch compared to the same thickness cotton is barely noticeable. The force that pushes the ball out when fired is thousands of pounds.
The purpose of PRB (patched round ball) is to have the lands of the rifling grab the ball tight enough to be consistently accurate and with enough bulk in the patch to seal the gas behind the PRB to provide consistent range/ vertical accuracy.
The truth is found only at the range firing from a bench, with rest, at paper, and collecting and examining fired patching. Try swaged comercial balls .570 to .575 and cotton patching ,010 to .020 with a charge 50-70 grs FFG black powder to start. Hunting loads are a different subject.
If you can load your PRB with thumb pressure it is too loose (use larger ball). If it takes a mallet to load or the patch shows cuts from the rifling it is too tight. A slap of the hand on a ball starter (that does not hurt) is about right. If the patch shows burned thru scorch marks it is too thin.
Find a shooting area with other BP shooters, They will all be happy to help, but take all opinions with a grain of salt. Good luck and have fun! If it gets frustrating get out your .22 or pellet gun and come back another day.