I used to shoot a once a week indoor IDPA style match. I went to IDPA Nat's in 2007, won my class in my division, and was subsequently banned from that indoor range when I got back home. Anywhooo...despite all the rumor mongering amongst all the St. Louis area shooters, it turned out to be a blessing in disguise. I picked up casting boolits and dropping my own bird shot, but not shooting those indoor matches anymore is what really made my lead levels drop. They were in the low 20's, and now they are in single digits, even though I still cast boolits and make birdshot.
Just like snorting coke, the quickest way to get anything into your system is to aerosolize it and then inhale it. That is exactly what you're doing at a crappy indoor range.