When I would take the 9.3x74R barrels out of the safe after long storage periods. I would notice the slightest bit of rust starting to develope under the sliding barrel band that adjusts the regulation of the barrels. After cleaning it off and spaying it with penetrating oil, it seems to happen again anyway. The answer was to coat that band with
Guard-it. Like a spray grease, if air can't get to it, it can't rust. That was the only problem that developed, I believe from using that gun in a wet environment and not cleaning it really well.