Of course we all know that Glock officially advises against the use of lead bullets in their pistols. I was talking with one of their techs one day a few years ago, and he gave me a different, unofficial view, and requested that he not be named (which I've forgotten anyway). What he told me is that lead bullets are OK if:
1. Keep the velocity down.
2. Use hard cast lead bullets - not pure lead swaged ones.
3. Clean the lead out as best you can before shooting jacketed ammo.
4. Don't start with the hottest jacketed loads you can find right after shooting lead.
I haven't done it myself because I found years go the lubed, cast bullets dirty a semi auto way more than jacketed ones, and I just never felt the need to shoot lead. But his thoughts do sound like common sense to me.
I shoot a lot of lead bullets out of revolvers, and I learned a little trick a couple of decades ago. After shooting lead, shoot some real hot jacketed ammo through the revolver - all charge holes in the cylinder at least two shots each. Blows the lead right out and makes cleaning much easier. This is exactly what you DON'T want to do with a Glock!