I found that patches, especially tight ones
are not unlike a buffing wheel. Rounding of lands is easy.
Thats why I use an undersized jag tip (7mm size for .30 bores) and a thick felt like material, which I got many years ago at an auto supply store.
The felt is loose enough that any grit caught up in it won't be pushed hard against the steel.
A loop type end can cause problems if the patch is dragged back in the bore, the forwards end can let the patch double on itself, especially bad if the patch escapes the muzzle even by a fraction.
Don't know if I'm right but I prefer to push until the patch is near even with the muzzle then pull back when swabbing with solvent, and only push all the way through when pushing out residue.
When brushing I generally squirt plenty of solvent, Ballistol usually, and make several ful length passes then sluice the initially broken away crud out holding the muzzle down with a long spray of the same, or sometimes a thin penetrating oil.
When the fouling is thick and old I use gasoline and push the brush through into a can of gas to rinse away crud at each pass and draw fresh gas in with the brush.
I have some synthetic "Hair Pad" material left over from repairing the seats of show horse saddles, I think its dacron but not sure.
If theres a lot of softened residue I sometimes put a patch of this in a loop and using plenty of solvent use it to gently scrubb the bore, rinsing out the patch after every pass and replacing it every few passes. Then when I'm sure no grit is left I use the jag and felt.
I also have
cleaned a few new unfired barrel. patches are nearly always grey.
I've cleaned new barrels and found them as dirty as if fired, perhaps not properly cleaned after a factory test firing.
My Savage .22 with synthetic stock had a bore full of fine black dust which appeared to be dust from the manufacture of the stock, probably caught in crannies in the stock and migrating into the bore during shipping.
I've used a number of polishing compounds in cleaning up old knives and in metal finishing of various sorts. A black waxy or greasey residue on the rags is likely atomized steel mixed with the waxlike materials that hold the solid blocks of compound together.
I've found J&B is a lot more abrasive than its supposed to be, at least with older softer steels.