I have a G21 and I would like to start shooting lead rounds through this gun (maybe 200–400 per month). At the advice of a few,I was told to get an aftermarket barrel such as Lone Wolf before I start shooting lead through my Glock.
I'd work up some test loads using hardcast lead bullets and try them out in your OE Glock barrel. Keep an eye on leading and test to see how accurate they are. My $.02.