If these are patches for cleaning the rifle, they really should not make all that big a difference. If these are patches to run ball, they still will not really make a difference. I have shot a lot of .54-.56 patch with .50 caliber roundball. If they do look too big you can always snip them at the muzzle with a scissors.

When you load and shoot a bigger patch, you will see them open up sooner and kind of float down to earth.. accuracy should not be all that different, but keep us posted.