I get the 41 cal brushes in bulk from Sinclair International and they measure out at about .45 for a good firm fit in the 404. Mostly I use the nylon brush with a patch round it and never leave the cleaning till it is so bad it need lost of scrubbing. A patch with Hoppes for the initial carb-powder clean then Bore tech CU for the copper, finish with Hoppes and let it stand overnight. Never needed anything more severe than that, although as Eagle 27 says some times after a bit of cast bullet playing a bristle brush with hoppes is used.

Von Gruff.