Varmint Al's testing, listed on his web site, showed that moisture could get underneath the moly coating and develop barrel rot in a standard 4140 CM barrel. Stainless barrels, however, aren't susecptable to this.
: Due to his findings, it is suggested that a CM barrel that is shot with moly coated bullets, be cleaned each day to prevent this from happening.
: XLC's pruduced no buildup that I could see or remove. They aren't moly coated and deliver excellent accuracy from the 2 rifles I tested them in.
: Some rifles require a bunch of molied shots to re-condition the bore after shooting bare bullets.
: Some then require a bunch of shots of bare bullets, to clean out the moly before they group properly.