Some guys have trouble, it seems in reading patches. The heavier the load, the more fraying there will be around the outside of a patch, due to muzzle blast from the increased pressure. The contact area around the ball should be VERY visible - compressed cloth fibers and have no burns or scorch marks running from beneath the ball, past the area of contact between the lands and grooves with the ball. If too thin a patch is used, powder flame will scorch the patch past the ball out towards the periphery of the patch - or burn it to black patches or fragments of charred cloth.
Many are the degrees of 'fit' in a patch and ball combination. Just for a test case, I have used in the .36 and .50 rifles, ball and patch combinations that do not run to the bottom of the grooves, patches showing scorches or burn marks, but still shooting 'cleanly', in that no wiping is necessary at any time. What these combinations showed, was that although shooting seemingly as cleanly as tighter combinations that sealed, these looser combinations were not as accurate - they loaded slightly easier (a VERY minimal difference though) but did not shoot as well. It all amounts to what is good enough for you.
If the patch is not reusable for at least another shot, it is not thick enough for the ball that is being used, in my opinion.
Using .030" patches in my .69, I can shoot a 5 shot group with the same patch, re-lubing it for each load. That is a patch that holds it's integrity.
In thinner combinations, though the patch might not be burnt or scorched, it still might not be the right combination for the gun - thus, we experiment to find what is the best if THAT is the goal.
1 1/2" accuracy at 25 yards is not good accuracy for any rifle. 2" to 3" means something is horrifically wrong - I mean BAD!
Here is a 5 shot group at 28yards with a 20 bore smoothbore - 1 sight only, at the front. 5 shots in 1.783" ---- 4 shots into 1.126"