Rifles can shoot well with rough bores.
Don't get to crazy with getting all the shit out.
Get some rubber stoppers and plug the muzzle end fill the bore with some sort of penetrating oil. I like kroil fill it and let it sit. Drain and save the kroil its got plenty of life in it. I then wrap some of that copper choreboy https://www.walmart.com/ip/Chore-Bo...0783&wl11=online&wl12=850206007&wl13=&veh=sem around a worn brush and scrub...I flood the bore with cheap brake cleaner at that point. I have been using break free foaming bore cleaner for years just seems to work. Sweets and barnes copper remover does great also . I have all but gave up on any brush. The only ones that seem to hold up re the Brownells line stainless with the short stiff bristles.
i typically dont use brushes either, but this one MIGHT need it!
i also considered soaking the bore...i guess if YOU say so it's not a bad idea i read elsewhere on the interwebs that select few take issue with doing it. screw them.