I shoot thousands of rounds every day at an indoor range over a 10-12 hour period, 5 days a week, and I don't use a mask/respirator. If you have elevated lead levels from shooting a couple hours a day/week you should find another range immediately.
Most people are worried about breathing in lead particles, but it's the lead on your hands you should be worried about. Even if you can't see it, it's still there. How many times do you touch your face or rub your eyes at the range? EVer go out to eat immediately after a range trip? Use soap designed to remove lead.