I haven't had any approved gun solvents break down the nylon brushes. I use the Montana X-treme bore and chamber brushes, as the bristles seem to be thicker and more stout than other brands.
After first purchasing them (I think the store was out of any brushes made of metal in the caliber I needed), the difference was clear and astounding. When you run a bronze brush down the bore the first time, it "sets" to that bore size. Run a 9mm bore brush down a 9mm bore, then try cleaning a .38 or .357. It kinda works but like when my ex-girlfriend returned from a "girls night out", not as much grabby friction there.
Not so with the Montana X-treme brushes. The nylon springs back to the original diameter. Over time the ends of the bristles where the strands were snipped become not as sharp as when new but they still work.