I'm not certain but I thought the graphite reduced or prevented oxidation. I'm currently using Lawrence Magnum shot that was purchased back in 1986 and it looks as good as new; i.e.. no white pellets. It's been stored in my garage and kept dry but it is exposed to the Ohio winter & summer temperatures.
The only reason I can figure out is that it makes the shot easier to size at the factory and it will flow through our reloaders a bit better. Graphite is a dry powder and will not effectively inhibit formation of lead carbonate (the white coating that forms when lead get moist). I do not believe lead oxidizes readily when exposed to air at normal temperatures, but I really should review my old Chemistry book if I can find it.
Here's a question. Other than looking bad and potentially leaving a a powdery residue in the reloader, what is the negative about lead oxidation? Does it have a negative impact on shot patterns or velocity? I've got quite a bit of shot with oxidation on it, but wanted to ask if there are any negatives, other than cosmetic, to using it in my reloads.
BrowningGal- There are a couple of problems to watch for when reloading the shot that has gotten wet. First, some of the shot can stick together and plug up the shot drop tube. Also, this shot will produce a dust when it is poured into the hopper. Stay away from this dust.
I once poured a bag of shot that had lead carbonate covering it. I saw the dust rise from the hopper so I left the room for a few minutes. I came back, the dust was gone so I felt safe. A week or so later I realized that the lead dust had settled on the table and was probably all over my hands. Lead dust is not our friend.
Thanks, Pat. I did use a dust mask so that any dust that came off the shot, when poured, didn't get into my lungs. Nice to know I did the right thing. I'll make sure I continue taking that same precaution as I work through the rest of my supply.