This is what I read about Moly on Sniper country
I have recently had misgivings about shooting moly bullets, and it seems there is growing evidence that these coatings should be avoided. I first had some indication that moly may contribute to bore corrosion in normal chrome-molybednum rifle barrels, when I saw "Varmint Al's" little unscientific test on his web page. He put some moly on a barrel surface, and left it for 24 hrs in a humid state. The barrel surface was slightly etched after only 24 hrs.
Now even more troublesome info is surfacing. If you contact Sinclair International to order something ask about their current disposition towards shooting moly or Danzac coated bullets. ( Sinclair is a leading precision shooters' suply store). It is notable that Sinclair sells moly coating products, as well as the Danzac coatings from Kincaid, Inc. At the present time Sinclair is advising people that they are not shooting moly or Danzac anymore in their own rifles, and are waiting for further info on the risks.
In the new shooting book written by Sinclair and Gravatt (who run Sinclair Int'l), there is a section on moly coating methods, etc. They say in their book that they cannot recommend using any bullet coatings at this time, and it is quite possible that moly will prove to be only the first generation of bullet coatings. They also relate some of the problems observed with moly use. The most significant and worrisome is that if moly is not completely cleaned out of a bore it builds up on itself....and....that a form of pitting and erosion has been observed underneath moly in *stainless steel* rifle barrels, that is unlike any pitting they have ever previously observed in this type of barrel.
For those who haven't shot moly bullets yet, be aware that it is nearly impossible to completely remove it from your barrel. You can get most of it with strong solvents, but bore paste (USP, JB's) will also be required to get nearly all of it out. It is alot of work. If you have already used moly, it is very important that it be removed as best you can after shooting. Do not put up guns which have been shot with moly, before you have given them a very thorough cleaning.
The guys I have talked to at Sinclair are now shooting plain old uncoated bullets, and being very careful to clean all the copper fouling out.