I recently found a plastic tub with 100 Sierra 338 cal 250 gr Match Kings, covered fairly thickly with Moly and some 300 grain SMKs coated with Tungsten Disulfide, that had been put in a box and left there for many years unintentionally. I usually tumble them in dry corn cob before putting them on the shelf, but forgot to with this batch.
On the Moly coated ones, when found, I figured, GREAT, some more boolits to launch without having to spend money! Sadly, when I took a close look at them I could see that the moly had created serious pits all over most of the bullets. There were also big chunks of Moly on some bullets that were very difficult to scrape off using a knife. I washed them off in Dawn and tumbled until there was no Moly left and they now look like someone hit them with a torch. Every one was discolored and deformed with craters and pits all over them. Crud. The batch of 300 grain SMK's coated with Tungsten Disulfide that were in the same location as the Moly batch, also still heavily coated with the Tungsten dust. I feared that they too were also ruined, but after tumbling a bit, to remove the stuck on excess powder, they looked PERFECT.
I knew that Moly can etch / pit barrel steel which is why I quit using it to coat bullets 6+ years ago, and switched to Tungsten Disulfide(?), but I had no idea it could eat away at copper like that. I am going to use them for foulers most likely rather than giving them a proper burial. So, if any of you are still using Moly, don't leave the bullets in the powder too long or you might regret it.
The photo link below shows what they looked like. Top bullet is a Berger for comparison, middle is the 250 SMK destroyed by Moly, bottom is a 300 gr SMK that was handled virtually the same as the 250 but was coated with Tungsten.
http://imgur.com/yCPOKWm
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