I have the same problem with my CZ-858 barrel. The only way (I can't clean it on the range) is to drive home, pour windex down the barrel, let it sit, spray the ENTIRE RIFLE, and I mean everything, with Windex, then use a bristle brush and patches to put copious amounts of nitro powder solvent in the barrel, and clean all parts using both the windex and nitro powder solvent. The clean the windex and nitro powder solvent out of the barrel and all parts, and apply oil, reassemble, and spray oil into the action and all moving parts. That way, only the barrel will rust.