I have used a mixture of hdydrgen proxid and white vinager 50 50 mix.
This will remove lead deposits from everything ie: scope lens, barrel mounts.
!!!CAUTION !!! THIS CAN DO DAMAGE TO SOME TYPE OF FINISHING!!
My comp and barrel are stainless and fit in a Zip lock baggie. let it soak for a few minnits depending on how dirty it is. Works great