While metalic lead can "disolve" into water (we don't use it in plumbing anymore), the amount leached into ground water or runoff is probably insignificant. Some rounds might either disingrate into fine particles or have fine particles dispursed at contact. These might be carried with a rapid flow of water, but again would probably settle out rather quickly.
The main problem in the US (as I understand it) has been with animal ingestion (ducks, etc. eating the lead shot) and subsequent death or illness from lead poisoning. I would suspect that some animals (primarily fish) with regular exposure to particulate lead would absorb enough to cause damage up the food chain.
I expect that the key question will be how much contamination your range contributes and whether it presents a continuing risk to the food chain. Always remember that the above represents two distinct questions.
We had something similar in Skagway, Alaska a few years ago. There was a lot of off loading of lead bearing ore there and a lot of resultant dust. Folks got all excited about the risk of all that lead dust blowing around and the public health officials did repeated testing of children and adults for lead accumlation/contamination in the body, as well as tests of the ground water used for drinking. Zip. Nada. There was a fair amount of lead "blowing around" - it just wasn't doing any damage.
You could check with the Alaska Dept. of Health and Social Services for more information on the Skagway situation. (Alaska has a web site from which you can drill down to the correct officials to whom to present questions.)
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Jim Fox
